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A 
Text Book 
of 

ORGANIC CHEMISEEY 



WILLIE ALBSET HOYES 



H« Holt and Company, 
1903 

BEST YOKK. 



*4 



s3 PREFACE. 



uS 



An attempt is here made to present the fundamental 
principles of organic chemistry for the use of those begin- 
ning the subject. The most radical departure from the 
method of treatment adopted in other books treating of 
the same subject, consists in the dropping of the division 
into "fatty" and "aromatic " compounds, and in the adop- 
tion of what appears to the author a more fundamental and 
logical classification. This novelty of arrangement will, it is 
hoped, be found to be justified, partly by the fact that so 
many connecting links are now known between the two 
classes of bodies that they no longer stand isolated from 
each other ; and further it is believed that the new method 
of treatment brings out the important contrasts in chemical 
conduct for the two series fully as well as the old. 

One of the most serious difficulties in presenting this 
subject lies in the overwhelming and ever increasing mass 
of material at our disposal. It is no longer possible, within 
a reasonable compass, to present all classes of compounds 
even, and important compounds of a given class must often 
be omitted. No two authors would make the same selection, 
and that here given is doubtless open to just criticism at 
some points. 

While the amount of material given is very small in com- 
parison with that to be found in large text-books, the reader 
will find many details which it is impossible for the most 



iv PREFACE. 

conscientious student permanently to retain in his memory. 
The student is advised, however, to read all of the book as 
well as thoroughly to master, by careful study, some portions 
of it. The attentive reader will, by this means, gradually 
absorb many ideas by a process which is closely akin to the 
acquisition of a language by a child. Only by a combina- 
tion of the two processes, intensive study of particular topics, 
and extensive reading in varied fields, can a satisfactory 
knowledge of any science be acquired. 

In study, the student should cultivate especially the habit 
of connecting all new facts with those which have been pre- 
viously presented. It is not a series of isolated facts which 
must be acquired, but a clear grasp of logical relationships. 
To illustrate : the statement will be found that the ethyl 
ester of carbostyril is prepared by heating the silver salt with 
ethyl iodide. The fact in itself is of no consequence ; but 
the thoughtful student should recognize that this is simply 
an application of one of the general methods previously 
given for the preparation of esters, and that, in reality, there 
is no new fact here to be learned, but that, instead, an old 
fact has been recalled for the purpose of fixing it more firmly 
in the memory. 

By such a process the attentive student gradually acquires, 
in the study of text-books and by reading the larger litera- 
ture, the ability to recognize methods which are unusual or 
striking. This ability, together with the power, which 
comes later, of recognizing whether -a new method is likely 
to be useful in other cases, is of fundamental importance to 
all those who wish to pursue the subject beyond its elements. 
It is partly for this reason that care has been taken, in 
almost every instance, to give those methods of actual prepa- 
ration which have been found best for individual compounds. 
Though, in some few cases, a general method of preparation, 



PREFACE. V 

or one which throws a clear light on the structure of a com- 
pound, has been selected instead of a better practical method 
which seemed too unusual in its character. 

A satisfactory knowledge of organic chemistry cannot be 
acquired from, a text-book or from lectures alone. A large 
amount of laboratory work is also required. Hints for the 
direction best given to such work are appended to the 
individual chapters of the book. These should be carried 
out with the aid of some of the books on organic work in 
the laboratory and with reference to the literature. With 
small classes it is usually best to assign different topics to 
different individuals and expect each to familiarize himself 
with the work the others are doing. 

In conclusion I wish to express my sincere thanks to 
Dr. J. Bishop Tingle and to Dr. A. M. Patterson, who have 
read the book in manuscript and who have offered many 
valuable suggestions ; to President W. E. Stone, who has 
read the chapter on carbohydrates ; to Professor J. H. Long, 
who has read the chapter on Compounds of Interest in 
Physiology and Pathology ; and to Dr. J. Bishop Tingle 
and Professor Alexander Smith, who have read the proofs. 
Thanks are also due to The Chemical Publishing Co., 
who have kindly permitted the use of several cuts from my 
" Organic Chemistry for the Laboratory." 



CONTENTS. 



INTRODUCTION. 

Definition, i. Source of carbon compounds, i. Structural formulae, 4, 
Classification, 6. 



CHAPTER I. 

PURIFICATION, ANALYSIS, DETERMINATION OF MOLECULAR 
WEIGHTS AND FORMULAE. 

Purification, 8. Crystallization, 8. Melting-point, 10. Distillation, 12. 
Fractional distillation, 13. Distillation under diminished pressure, 
16. Steam distillation, 17. Boiling-point, 18. Analysis, 19. Em- 
pirical formulae, 2 1 . Determination of molecular weight, 22. Vapor 
density; Dumas's method, 23. Victor Meyer's method, 25. Hof- 
mann's method, 26. Determination of molecular weights by the 
freezing-point method, 26, Boiling-point method, 32. Determina- 
tion of molecular weights by substitution products, 37. Laboratory 
exercises, 38. 



CHAPTER II. 

PHYSICAL PROPERTIES. 

Specific gravity, 39. Molecular volume, 40. Surface tension, 43. Vis- 
cosity, 43. Critical temperature, 44. Specific heat, 44. Heat of 
combustion, 44. Heat of formation, 45. Molecular refraction, 46. 
Molecular dispersion, 47. Color, 47. Circular polarization, 47. 
Magnetic molecular rotation, 49. Electrical conductivity, 49. Lab- 
oratory exercises, 54. 



Vlll CONTENTS. 



CHAPTER III. 



HYDROCARBONS. MARSH-GAS SERIES. 

Table of paraffins, 56. Homology, 56. Methane, 58. Ethane, 61. 
Propane and its substitution products, 62. Isomerism, 64. Graph- 
ical formulae, 65. Arrangement in space, 66. Butanes, 66. Pen- 
tanes, 67. Hexanes, 68. Official nomenclature, 68. Higher 
paraffins, 70. General properties of the paraffins, 70. Petroleum, 
71. Flashing-point, 73. Laboratory exercises, 74. 



CHAPTER IV. 

ETHYLENE SERIES. UNSATURATED HYDROCARBONS. 

Table of ethylene series, 75. Ethylene, 76. Unsaturated compounds, 
77. Structure of ethylene ; " Double unions," 79. Homologues 
of ethylene, 80. Nomenclature, 80. Physical properties, 80. Lab- 
oratory exercises, 81. 

CHAPTER V. 

CYCLIC HYDROCARBONS, C n H 2w - 

Table of cyclic compounds, 82. Cyclopropane, 83. Cyclobutane, 83. 
Cyclopentane, 84. Cyclohexane and cycloheptane, 85. Heat of 
combustion, 85. Occurrence of cyclic hydrocarbons, 86. Labora- 
tory exercises, 86. 

CHAPTER VI. 

SERIES C n H 2 „_ 2 > C„H 2H _ 4 , AND C n H 2n _ 6# 

Table of acetylene series, 87. Acetylene, 87. Structure of acetylene, 89. 
Nomenclature, 90. Series C n H 2n _4 and C„H 2 „_ 6 , 91. Terpenes, 
91. Laboratory exercises, 92. 



CHAPTER VII. 

BENZENE SERIES. 

Aliphatic and aromatic compounds, 93. Structure of benzene, 94. 
Ladenburg's prism formula, 101. Formula of benzene, 103. Ortho, 



CONTENTS. IX 

meta, and para positions, 105. Table of benzene series, 107. Ben- 
zene, 107. Toluene, 108. Xylenes, 109. Ethyl benzene, 109. 
Pseudocumene, no. Mesitylene, no. Cymene, no. Preparation 
of hydrocarbons of the benzene series, 1 1 1 . General characteristics, 
112. Laboratory exercises, 113. 



CHAPTER VIII. 

HYDROCARBONS RELATED TO BENZENE. 

Table, 114. Triphenylmethane, 115. Triphenylmethyl, 115. Naphtha- 
lene, 116. Anthracene, 117. Phenanthrene, 119. Laboratory 
exercises, 120. 

CHAPTER IX. 

CLASSIFICATION OF DERIVATIVES OF THE HYDROCARBONS. 

Table of derivatives, 121. 

CHAPTER X. 

ALCOHOLS AND PHENOLS. 

Table of alcohols and phenols, 124. Methyl alcohol, 126. Effect of the 
hydroxyl group, 1 29. Ethyl alcohol, 129. Theories of fermentation, 
129. Absolute alcohol, 132. Determination of alcohol, 132. Physi- 
ological effects, uses and chemical properties, 133. Propyl alcohols, 
134. Butyl alcohols, 135. Amyl alcohols, 136. Primary, secondary 
and tertiary alcohols, 136. Optical activity, 137. Separation of 
racemic compounds into their components, 138. Alcohols of the 
ethylene series, 139. Vinyl alcohol, 139. Allyl alcohol, 140. Cyclic 
alcohols, 142. Borneol, 142. Phenol, 142. Conductivity and 
dissociation of weak acids, 144. Chemical character of phenols, 
145. Cresol, 147. Benzyl alcohol, 148. Carvacrol and thymol, 148. 
Naphthols, 149. Alcohols containing two or more hydroxyl groups, 
149. Glycol, 150. Propylene glycol and trimethylene glycol, 
152.' Glycerol, 152. Nitroglycerine, 154. Erythrol, 154. Mannite, 
dulcite, sorbite, 158. Pyrocatechol, 158. Resorcinol, 158. Hydro- 
quinone, 160. Pyrogallol, 160. Phloroglucinol, 160. General meth- 
ods of preparing alcohols, 161. Laboratory exercises, 162. 



X CONTENTS. 

CHAPTER XL 

' ETHERS. 

Table of ethers, 164. Ethyl ether, 165 ; historical, 165 ; chemical con- 
duct, 167. Ethylene oxide, 168. 

CHAPTER XII. 

ALDEHYDES AND KETONES. 

Table of aldehydes, 170. Table of ketones, 171. Definition of alde- 
hydes and ketones, 173. Nomenclature, 173. Formaldehyde, 173. 
Acetaldehyde ; structure, 175. Polymeric forms, 176. Condensa- 
tion of aldehyde ; aldol, 177. Derivatives of acetaldehyde, 178. 
Oxidation and reduction of aldehyde, 180. Acrolein, 180. Cro- 
tonic aldehyde, 181. Geranial or citral, 181. Benzaldehyde (oil of 
bitter almonds), 182. Benzaldoxime, 183. Stereoisomerism of 
nitrogen compounds, 183. Condensation of benzaldehyde, 184. 
Salicylic aldehyde; the Reimer-Tiemann synthesis, 185. Vanillin, 
186. Piperonal, 187. Acetone, 187. Derivatives of acetone, 189. 
Condensations with ketones, 190. Formation of mesitylene, 191. 
Mesityl oxide and phorone, 192. Cyclopentanone and cyclohexanone, 
192. Formation of rings, 193. Oxidation of cyclic ketones, 194. 
Camphor, 195. Compounds isomeric with camphor, 197. Irone 
andionone, 197. Acetophenone, 198. Benzophenone, 199. Beck- 
mann's rearrangement, 200. 1,2-Diketones, 204. Diacetyl, 203. 
Benzil, 203. Phenanthrenequinone, 204. 1,3-Diketones, 204. Acet- 
ylacetone, 206. i-Phenyl-2,5-pyrazole, 206. Dihydroresorcinol, 
207. Acetonylacetone, 207. Dimethylfurane, 208. Quinones, 209. 
Benzoquinone, 209. p-Xyloquinone, 211. Anthraquinone, 211. 
Alizarin, 212. Derivatives of anthracene, 214. General methods of 
preparing aldehydes, 215. General methods of preparing ketones, 216. 
General characteristics of aldehydes and ketones, 218. Labora- 
tory exercises, 219. 

CHAPTER XIII. 

ACIDS. 

Structure, 220. Definition of cm acid, 221. Table of fatty acids, 222. 
Formic acid, 223. Acetic acid, 225. Salts of acetic acid; acid 



CONTENTS. XI 

salts; decompositions, 227. Uses, 228. Propionic acid, 228. 
Butyric acids, 229. Isovaleric, palmitic, and stearic acids, 230. 
Soap, 230. Structure of natural fatty acids, 231. Table of acids, 
C n H 2n _20 2 , 232. Acrylic acid, 233. Crotonic acid, 234. Isocro- 
tonic acid; alloisomerism, 235. Stereoisomerism, 236. Hydrosor- 
bic acid, 237. Oleic and elai'dic acids, 238. Stereoisomerism of 
cyclic compounds, 239. Table of acids, C n H 2re _ 4CV 240. Table 
of aromatic acids, 240. Benzoic acid, 241. Oxidation of deriva- 
tives of benzene, 242. Cinnamic acid ; Perkin's synthesis, 244. Phen- 
yl propiolic acid ; indigo, 247. Table of bibasic acids, 248. Oxalic 
acid, 249. Malonic acid, 251. Condensations with malonic ester, 
252. Succinic acid, 254. Isosuccinic acid, 255. Glutaric acid, 255. 
Adipic acid, 256. Pimelic acid, 257. Fumaric and malei'c acids, 
257. Mesaconic, citraconic, itaconic, and glutaconic acids, 258. 
Hexahydroisophthalic acid, 258. Camphoric acid, 258. Isocam- 
phoric and camphanic acids, 260. Campholytic acids, 261. Phthalic 
acid, 261. Phthalonic acid, 261. Phthalic anhydride, phthalyl chlo- 
ride, and phthalid, 262. Phenol phthalein, 263. Fluorescein, 264. 
Eosin, 265. Isophthalic and terephthalic acids, 265. Reduction 
products of terephthalic acid, 266. Use of the phthalic acids in 
determining the structure of aromatic compounds, 268. General 
methods of preparing acids, 270. Laboratory exercises, 271. 



CHAPTER XIV. 

DERIVATIVES OF ACIDS. 

Acid chlorides, 273. Acetyl chloride, 276. Benzoyl chloride, 276, 
Acid anhydrides, 276. Acetic anhydride, 277. Phthalic anhydride 
278. Esters, 278. Preparation of esters, 278. V. Meyer's law of esteri 
fixation, 280. Saponification, 283. Diethyl carbonate, 284. Mono 
ethyl carbonate, 284. Orthocarbonic and orthoformic esters, 285 
Acetal, 285. Chlorformic or chlorcarbonic ester, 286. Amides 
286. Structure of the amides, 287. Amido and amino groups, 289 
Imides, 289. Urea or carbamide, 290. Carbamic acid and carbarn 
ic chloride, 292. Urethane, 292. Phenyl urethane, 293. Uric acid 
293. Alloxan, 293. Alloxantin, 294. Parabanic acid, 294 
Structure of uric acid, 294. Tautomeric compounds, 297. Xan- 
thine, theobromine and caffeine, or theine, 298. Guanine, 299 



xii CONTENTS. 

Acetamide, 299. Benzamide, 299. Phthalamidic acid, 299. Cyan- 
ides or nitriles, 300. Hydrocyanic acid, 302. Cyanogen chloride, 
303. Isocyanides or isonitriles, 304. " Carbylamines," 304. Cyan- 
ates and isocyanates, 306. Ethyl cyanate, 306. Ethyl isocyanate or 
ethyl carbonimide, 307. Phenyl isocyanate, 307. Fulminic acid, 308. 
Thiocyanates, 308. Potassium, ammonium, and ethyl thiocyanates, 
308. Isothiocyanates or mustard oils, 309. Allyl thiocyanate, 310. 
Amide chlorides, imide chlorides, and imido esters, 310. Amidines 
and amidoximes, 311. Laboratory exercises, 311. 



CHAPTER XV. 

HYDROXY ACIDS. 

Definition, 313. Carbonic acid, 313. Glycolic acid, 313. Esters and 
ethers of glycolic acid, 315. Glycolid, 315. Lactic acids, 315. 
Lactid, 317. /3-Hydroxypropionic acid, 317. /3- and 7-Hydroxy- 
butyric acids, 318. Butyrolactone, 319. 7-Hydroxyisocaproic acids 
319. Acids, C„H 2w _ 2 3 , 320. Acids, C n H 2n _ 6 3 , 321. Sali- 
cylic acid ; Kolbe's synthesis, 321. Metahydroxybenzoic acid, 323. 
Parahydroxybenzoic acid, 324. Anethol, 324. Phthalid, 325. 
p-Hydroxyisopropyl benzoic acid, 325. Acids, C„H 2n 4 , 325. Glyox- 
ylic acid, 325. Glyceric acid, 326. Glycidic or epihydrinic acid, 326. 
Dihydroxystearic acid, 327. Tartronic or hydroxymalonic acid, 327. 
Mesoxalic acid, 328. Malic acid, 328. Condensations with malic 
acid; coumarin, 330. Tartaric acid, 331. Citric acid, 335. Aco- 
nitic, itaconic, and citraconic acids, ^37- Acetone dicarboxylic acid, 
337. Saccharic acid, 338. Mucic acid, 339. Dehydromucic acid, 339. 
Protocatechuic acid, 339. Gallic acid, 340. Tannin, 341. General 
methods of preparing hydroxy acids, 341. General properties of 
hydroxy acids, 341. Laboratory exercises, 343. 



CHAPTER XVI. 

KETONIC AND ALDEHYDE ACIDS. 

Glyoxylic acid, 344. Pyroracemic acid, 344. Phenylglyoxylic acid, 346. 
Phthalonic acid, 346. Formyl acetic acid, 346. Acetoacetic acid 
and ester, 347. Ketone and " enol " forms, 349. Condensations 



CONTENTS. xili 

with acetoacetic ester, 350. Acid and ketonic decompositions, 351. 
Carboxethyl cyclopentanone, 352. Carboxethyl cyclohexanone, 354. 
Succiny] ©succinic ester, 354. Dioxyterephthalic ester, 355. Levu- 
linic acid, 355. Angelica lactones, 356. Laboratory exercises, 356. 



CHAPTER XVII. 

CARBOHYDRATES. GLUCOSIDES. 

Table of the carbohydrates, 357. Definition, 358. Tetrose, 359. 
Arabinose and xylose, 360. Glucose or grape sugar, 361. Struc- 
ture of glucose, 362. Synthesis of glucose, 363. Glucosazone, 364. 
Fructose or fruit sugar, 365. Configuration of sugars, 366. Inosite, 
367. Saccharose or cane-sugar, 367. Lactose, 370. Maltose, 370. 
Trisaccharides ; raffinose, 371. Cellulose, 371. Gun-cotton, 372. 
Starch, t>73- Dextrin, 374. Glycogen, 374. Inulin, 374. Arabin, 
xylan, 375. Glucosides, 375. Aesculin, 375. Amygdalin, 376. 
Coniferin, 376. Digit alei'n, 376. Tannins, 376. Indican, 376. 
Iridin, 377. Myronic acid, 377. Phlorizin, 377. Salicin, 378. 
Saponin, 378. Solanine, 378. Bitter principles, 378. Laboratory 
exercises, 379. 



CHAPTER XVIII. 

HALOGEN COMPOUNDS. 

Methods of preparation, 380. Laws of positions taken by substituting 
groups, 363. Halogen substitution products of acids, 385. General 
properties of halogen compounds, 389. Differences between aromat- 
ic and aliphatic halogen compounds, 391. Reduction of halogen 
compounds, 392. Halogen derivatives of acids ; a-Halogen acids, 392. 
/3-Halogen acids, 393. 7-Halogen acids, 394. Methyl iodide, 395. 
Methylene iodide, 395. Iodoform, bromoform, and chloroform, 396. 
Fatalities with anaesthetics. 397. Carbon tetrachloride, 397. 
Ethyl chloride, 398. Chlorine derivatives of ethane, 398. Ethyl 
bromide, 399. Ethylene bromide, 399. Bromethylene or vinyl 
bromide, 399. Perbromethylene, 399. Ethyl iodide, 400. Nor- 
mal and isopropyl iodides, 400. Allyl bromide, 2-brompropene and 
3-brompropene, 400. Trimethylene bromide, 401. Pinene hydro- 



Xiv CONTENTS. 

chloride, 401. o-Bromtoluene, 401. m-Bromtoluene and p-Brom- 
toluene, 402. Benzyl bromide, 403. Triphenylchlormethane, 403. 
Chlorhydrins, 403. Glycol chlorhydrin, 404. a-Monochlorhydrin, 
404. s-Dichlorhydrin,405. Trichlorhydrin, 405. 2, 4, 6-Tribromphen- 
ol, 405. Chloral or trichloraldehyde, 405. Monochloracetic acid, 
407. Dichloracetic acid, 408. Trichloracetic acid, 408. Histori- 
cal' importance of trichloracetic acids, 408. Dissociation constants 
of the chloracetic acids, 409. a-Brompropionic acid, 409. /3-Iodo- 
propionic acid, 409. Orthobrombenzoic acid, 410. m-Brombenzoic 
acids, 410. p-Brombenzoic acid, 410. Laboratory exercises, 410. 



CHAPTER XIX. 

NITRO COMPOUNDS. 

Ethyl nitrite, 411. Nitroethane, 411. Salts of the nitroparaffins ; 
pseudo acids, 411. Nitrobenzene, 413. m-Dinitrobenzene, 414. 
s-Trinitrobenzene, 414. Nitrotoluenes, 414. Phenylnitromethane, 
415. Nitroxylenes, 415. a-Nitronaphthalene, 416. Nitrophenols, 416. 
Nitrobenzoic acids, 416. Dissociation constants of the nitrobenzoic 
acids, 417. o-Nitrocinnamic acid, 418. o-Nitrophenylpropiolic acid, 
418. Nitrourea, 418. Semicarbazine, 419. Laboratory exercises, 
419. 

CHAPTER XX. 



Definition ; primary, secondary, and tertiary amines, 420. Methods of 
preparing amines, 420. Properties of the amines ; "strength," 423. 
Effect of nitrous acid on amines, 425. Nitrosamines, 426. Lieber- 
mann's reaction, 427. Formation of isocyanides or isonitriles, 427. 
Hinsberg's method of distinguishing primary and secondary 
amines, 428. Alkyl thiocarbamic acids ; isothiocyanates, 428. 
Methyl amine, 429. Dimethyl amine, 429. Trimethyl amine, 430. 
Tetramethyl ammonium iodide, 431. Ethyl amines, 431. Asym- 
metry of nitrogen compounds, 432. Vinyl amine or dimethyl imine, 
432. Vinyl trimethyl ammonium hydroxide (neurine), 433. Ethylol 
trimethyl ammonium hydroxide (choline), 433. Pentamethylene 
diamine (cadaverine), 433. Piperidine (hexazane or hexahydro- 



CONTENTS. XV 

pyridine), 434. (n)-Methyl piperidine, 435. /3-Methyl piperidine 
(a-pipecoline ), 435. Coniine, 435. Pyrrol, 436. Pyrroline and 
pyrolidine, 437. Pyridine, 437. Picolines and lutidines, 438. 2 
4,-6-Trimethyl pyridine (7-collidine), 438. Nicotine, 438. Aniline : 
439. Acetanilide (antifebrine), 440. Methyl aniline, 441. Di 
methyl aniline, 442. Methyl violet ; rosaniline ; fuchsine, 442 
Toluidines and xylidines, 442. Benzyl amine, 443. Phenylene di 
amine, 443. a-Methylbenzimidazole, 443. p-Phenylene diamine 
444. Benzidine, 444. a-Naphthylamine, 444. Ar-tetrahydro-a 
naphthylamine, 445. Ac-tetrahydro-a-naphthylamine, 445. Quin 
oline, 446. a -Methyl hydroxylamine, 447. /3-Ethyl hydroxylamine 

448. Glycocoll (glycine or aminoacetic acid), 448. Sarcosine, 449 
Trimethyl glycocoll (beta'in), 449. Hippuric acid (benzoylglycocoll) 

449. Alanine ( a -aminopropionic acid), 450. Leucine (cc-amino 
caproic acid), 450. a-Asparagine (a -aminosuccinamidic acid) 

450. Anthranilic acid (o-aminobenzoic acid), 451. o-Amino-a 
toluic acid ; oxindol ; dioxindol; indol; isatine ; indigo, 451. o-Am 
ino hydrocinnamic acid, 452. Carbostyril (py-2-hydroxyquinoline) 
453. Ethyl ester of carbostyril ; ethyl pseudocarbostyril, 454 
Laboratory exercises, 455. 



CHAPTER XXI. 

DIAZO, AZO, HYDRAZO, AND OTHER NITROGEN COMPOUNDS. 

Structure of diazo compounds, 456. Replacement of the diazo group, 459 
Replacement by hydrogen, 459. Replacement by hydroxyl, 460 
Replacement by halogens, 460. Replacement by cyanogen, 461 
Replacement by hydrocarbon residues, 462. Replacement by sul 
phur, the sulphonic, nitro, and other groups, 462. Diazoacetic ester 
462. Diazoacetic acid ; triazoacetic acid, 463. Diazoamino com 
pounds, 464. Diazoamino benzene, 466. Aminoazo compounds, 466 
p-Aminoazobenzene, 467. p-Dimethylaminoazobenzene, 468. 4 
Sulpho^'-dimethylaminoazobenzene (Helianthin, Orange III, Tro 
paolin D), 468. p - Sulphobenzene-azo- a -naphthylamine, 469 
Hydroxyazo compounds, 469. p - Hydroxy azobenzene, 470 
4-Sulpho- 2 / ,4 / -dihydroxyazobenzene, 47 r. Azoxy compounds, 47 
Azobenzene, 473. Hydrazo compounds, 473. Benzidines; semi 
dines, 474. Disazo compounds, 475. Hydrazobenzene, 476. Hy 



xvi CONTENTS. 

drazines, 476. Phenylhydrazine, 477. Hydrazones ; osazones, 
478. Diazoimides, 478. Diazobenzenimide (triazobenzene, phenyl 
cyclotriazine), 479. Dyes, 479. Chromophor groups; auxochrome 
groups, 480. Mordants, 481. Substantive and adjective dyes, 481. 
Other auxiliary groups, 481. Fast colors, 482. Laboratory exer- 
cises, 482. 

CHAPTER XXII. 

SULPHUR COMPOUNDS. 

Mercaptans or thioalcohols, 483. Ethyl mercaptan (ethanethiol), 483. 
Thiophenol, 484. Sulphides or sulphur ethers, 484. Ethyl sulphide, 
484. Acetone ethylmercaptol (dithioethyl-dimethylmethane), 485. 
Phenyl sulphide, 485. Sulphones, 486. Diethylsulphone, 486. 
Diethylsulphone-dimethylmethane (sulfonal), 486. Diphenylsul- 
phone, 486. Sulphonium bases, 487. Triethyl sulphonium iodide, 
487. Methylethylthetin bromide ; asymmetric sulphur compounds, 
487. Sulphonic acids, 488. Structure of the sulphonic group, 489. 
Ethyl sulphonic acid, 490. Benzene sulphonic acid, 491. o-Sulpho- 
toluene, 491. Toluene sulphamide ; benzoic sulphinide (saccharin), 
492. Naphthalene sulphonic acids, 493. Anthraquinone-2 -sul- 
phonic acid, 493. The sulphonic acid of acetic acid, 494. Labora- 
tory exercises, 494. 

CHAPTER XXIII. 

HETEROCYCLIC COMPOUNDS. 

Thiophene, 495. Coumarin, 496. Coumarone, 497. Pyrazole, 497. 
i-Phenylpyrazole, 498. Pyrazolone, 498. i-Phenyl-3-methylpyra- 
zolone, 499. i-Phenyl-2,3-dimethylpyrazolone (antipyrine), 499. 
Acridine, 499. Acridone, 500. Laboratory exercises, 501. 



CHAPTER XXIV. 

ALKALOIDS. 

Definition, 502. Pyridine group, 503. Pilocarpine, 503. Conii'ne, 503. 
Nicotine, 503. Atropine, 503. Cocaine, 504. Connection between 



CONTENTS. XVll 

structure and the physiological effect of cocaine, 504. Ecgonine, 505. 
Quinoline group, 505. Quinine, 505. Cinchonine, 506. Quinidine, 
506. Strychnine, 506. Brucine, 506. Isoquinoline group, 506. Lauda- 
num, 507. Hydrastine, 507. Berberine, 507. Alkaloids of un- 
known structure ; veratrine, 508. Jervine; gelsemine; aconitine ; 
emetine; lobeline ; solanine, 508. Laboratory exercises, 508. 

CHAPTER XXV. 

COMPOUNDS OF INTEREST IN PHYSIOLOGY AND PATHOLOGY. 

Proteins; classification, 509. Albumins, 510. Lysine or a,e-diamino 
caproic acid, 512. Globulins, 512. Fibrin, 513. Nucleoalbumins, 

513. Casein, 513. Albumoses and peptones, 513. Nucleoprotei'ds, 

514. Haemoglobin, 514. Glycoproteins, 515. Collagens, 515. 
Keratins, 515. Elastins, 515. Enzymes or soluble ferments, 516. 
Ptomaines, 517. Tetanine; typhotoxine ; erysipeline, 518. Toxins, 
518. Antitoxins, 519. Fats, 519. 



INTRODUCTION. 



In its origin the term Organic Chemistry implies a science 
which discusses the compounds that are found in, or derived 
from, organized or living bodies. There was, at one time, a 
general opinion that such compounds differed in some man- 
ner from others, and that they resulted from the action of 
some occult vital force. As many of these bodies have been 
prepared from the elements by pure laboratory processes, 
such a view has long since become untenable, and no one 
now supposes that the chemical forces within the living plant 
or animal differ in any respect from those outside. A very 
large proportion, too, of the eighty thousand or more com- 
pounds known to the science have never been found in 
plants or animals. The name is retained in spite of these 
objections, partly because it is convenient from long, well- 
established usage, partly because animal and vegetable sub- 
stances still remain the practical source of most of those 
carbon compounds with which the student of organic chem- 
istry is concerned. . 

The natural source of the carbon compounds is the car- 
bon dioxide of the atmosphere. This is absorbed by plants, 
and the compounds required for vegetable growth are pro- 
duced by a process of reduction, accompanied by the evolu- 
tion of free oxygen, and a combination of the carbon with 
the elements of water. The energy absorbed in the pro- 
cess is very considerable, and this is furnished by the sun- 



2 INTRODUCTION. 

light. There seems to be some microscopic evidence that 
starch is one of the first products formed by the assimila- 
tion of the carbon ; and there is also good ground for the 
belief that the chlorophyl of the leaf is directly active in 
the process, but positive knowledge with regard to the 
chemical phenomena involved is very meager. 

The bodies which appear to be most closely connected 
with the phenomena of life, both in plants and in animals, 
are the proteins, compounds containing carbon, hydrogen, 
oxygen, nitrogen, and sulphur. But the knowledge of the 
chemistry of these bodies, to say nothing of the part which 
they undoubtedly play in the syntheses occurring within 
living bodies, is, at present, very unsatisfactory. This is 
owing to their extremely complex nature, and to the fact 
that very few of them can be crystallized, making it impos- 
sible to judge satisfactorily of the homogeneous nature, and 
so of the purity, of any one of them when prepared. 

The nitrogen of the proteins is furnished to the plant 
partly by the nitrates and other nitrogenous compounds of 
the -soil, and partly by the nitrogen of the air, which may, in 
some cases, be assimilated by the plant with the aid of 
micro-organisms which attach themselves to its roots. 

A great variety of compounds are formed in plants be- 
sides starch, cellulose, or woody fiber, and proteins. The 
most important classes of these compounds are the gums, 
sugars, fats or oils, acids and esters, all of which contain 
carbon, hydrogen, and oxygen ; the glucosides, which some- 
times contain nitrogen in addition ; the alkaloids containing 
carbon, hydrogen, and nitrogen, and frequently oxygen ; and 
the terpenes and volatile ("essential ") oils, which are mostly 
compounds of carbon and hydrogen, though the latter some- 
times contain oxygen. 

Chlorine, sulphur, phosphorus, silicon, sodium, magne- 



INTRODUCTION. 3 

sium, potassium, calcium, and iron are taken up from the 
soil, and are essential to the life and growth of most plants. 
The basic elements are found, in some cases, as a part of the 
salts of organic acids ; otherwise the nature of the com- 
pounds which these elements form and the part which they 
play in the plant growth is, with few exceptions, wholly un- 
determined. 

Animals must secure the carbon compounds required for 
their life and growth directly or indirectly from the sub- 
stances furnished by plants. In general the characteristic 
processes of plant life are reduction processes accompanied 
by an evolution of oxygen ; those of animal life, on the 
other hand, oxidation processes resulting in an evolution of 
carbon dioxide and the formation of urea, which may be 
considered as a compound of carbon dioxide with ammonia, 
less the elements of water. The plant growth, too, is mainly 
a synthetical process, accompanied by an absorption of 
energy ; animal life, a process associated with a decomposi- 
tion of complex compounds into simpler ones, and accompa- 
nied by an evolution of heat and mechanical energy. But 
while this is true in general outline, oxidation and evolution 
of carbon dioxide may take place in the plant, notably in the 
blossom and during the night ; and many synthetical pro- 
cesses occur in animal bodies. 

Under the influence of bacteria there are formed during 
processes of putrefaction, and also in connection with many 
forms of disease, basic compounds called ptomaines. These 
contain carbon, hydrogen, and nitrogen, and, frequently, 
oxygen. Other violently poisonous compounds, known as 
toxalbumins from their supposed relation to the proteins, or 
albuminous bodies,* are also formed in a similar manner. 

* Professor Vaughn, however, considers that these compounds are not albuminsi 
and designates them by the more general name toxins. 



4 INTRODUCTION. 

The life processes which have been sketched in the barest 
outline furnish the practical materials with which the science 
of organic chemistry has to deal. The problems with which 
it is concerned are : first, the separation of individual com- 
pounds in a pure state, followed by their analysis and a de- 
termination of their molecular weights; and, second, the 
study of the relations existing between these compounds, and 
the study of the compounds which may be prepared from 
them. As has already been stated, the derivatives now far 
exceed in number those compounds which have been ob- 
tained directly from living bodies. 

Structural Formulae. — Many of the relations existing 
among the carbon compounds find their most concise ex- 
pression in structural formulae. The principles which lie 
at the foundation of these formulae are : 

i. That a given atom in a compound is directly united to 
only a small number of other atoms, and that for each ele- 
ment this number never exceeds a certain amount which is 
known as the highest valence of the element. For carbon 
this highest valence is four. Whether the combination of 
atoms consists in their actual attachment to each other, or 
whether they are held by their mutual attractions in a state 
of vibration between narrow limits about points of stable 
equilibrium, or whether they are held in definite positions 
with regard to each other by the effect of their motions on the 
ether, and through that upon each other, are at present mat- 
ters of scarcely more than mere speculation. With such 
questions structural formulae have, at present, practically 
nothing to do, 

2. That in many reactions a group of atoms from one mole- 
cule becomes a part of a new molecule without any structu- 
ral change within the group. Thus, in the transformation 



INTRODUCTION. 5 

of acetic acid, C 2 H 4 2 , into acetyl chloride, C 2 H 3 O CI, the 
carbon, hydrogen, and oxygen atoms of the acetyl group, 
C 2 H 8 O, are supposed not only to hold together in passing 
from one compound to the other, but it is also supposed that 
they retain their order of structural arrangement ; that, for 
instance, a hydrogen atom which is attached to a given car- 
bon atom in acetic acid is attached to the same carbon atom 
in acetyl chloride. It does not follow from this that the 
mutual relations between the atoms within the group may 
not be greatly altered by the passage of the group from one 
compound to another. Thus a hydrogen atom in acetyl 
chloride may be more or less easily affected by some re- 
agents than the same hydrogen atom in acetic acid. In many 
cases differences of this sort are very marked. We are not 
even compelled to suppose that there is a set geometrical 
form which is retained by the group in the various com- 
pounds into which it enters. But an intelligent discussion 
of the facts of organic chemistry is not at present possible 
without the assumption of that maintenance of structural 
arrangement, or order of attachmeiit, within groups which is 
here stated. 

Groups of the kind here described are called radicals. 

3. It is usually assumed that when an atom or group 
leaves a compound and another atom or group enters it, the 
latter attaches itself at the point left vacant by the former. 
This principle is, in an important sense, merely a corollary 
of that last stated. 

In practically applying these principles for the determi- 
nation of the structure, or order of arrangement, of a given 
compound, two general methods may be used : the analytical 
method, which consists in breaking the compound down and 
identifying the various groups which it contains ; and the 
synthetical method, which consists in building up the com- 



6 INTRODUCTION. 

pound by putting together known groups. The second 
method is usually more satisfactory and conclusive. 

From the nature of the case, it often happens that the 
structure of a given group does not remain unchanged when 
it enters a new compound, and in such cases the results ob- 
tained in different reactions may be contradictory ; and it 
may be necessary to accumulate a large amount of evidence 
before a satisfactory conclusion can be reached. 

Classification. — In classifying the material of organic 
chemistry for the use of beginners in the science, a funda- 
mental difficulty is met. It is especially true in this science 
that no single compound can be understood without a knowl- 
edge of a considerable number of other compounds, and the 
relation to other compounds is usually the most important 
part of the knowledge which must be acquired. It is fre- 
quently necessary at the outset, therefore, to refer to com- 
pounds not previously described. 

The hydrocarbons are usually selected for first considera- 
tion because of the fundamental relation which they bear to 
all other compounds. One treatise on organic chemistry, 
indeed, calls the science that of the hydrocarbons and their 
derivatives. In the further classification it has been custom- 
ary to divide organic compounds into two groups, the alipha- 
tic or fatty acid compounds, and the aro7natic compounds, 
or benzene and its derivatives. 

One of the best of the larger text-books * adopts the fol- 
lowing closely related classification : 

i. Aliphatic, or open chain compounds. 

2. Isocyclic compounds, containing rings of carbon atoms. 

3. Heterocyclic compounds, containing rings composed of 
atoms of two or more kinds, as carbon and nitrogen, 
carbon and sulphur, etc. 

* Lehrbuch der Organischen Chemie, von Meyer und Jacobson. 



INTRODUCTION. 7 

The distinction between aliphatic and aromatic compounds 
has lost something of its force of later years, and an attempt 
has been made in the present work to return to a simpler 
and more logical classification. The hydrocarbons are con- 
sidered first, as heretofore, and all classes of them together. 
Then follow oxygen compounds and compounds containing 
halogens, nitrogen, and sulphur, and, finally, three chapters 
upon heterocyclic compounds, alkaloids, and compounds of 
physiological and pathological interest. 



ORGANIC CHEMISTRY. 



CHAPTER I. 

PURIFICATION, ANALYSIS, DETERMINATION 

OF MOLECULAR WEIGHTS, AND 

FORMULAE. 

The practical basis on which organic chemistry rests is 
the preparation and separation of homogeneous, or, as com- 
monly stated, pure substances, and the determination of 
their physical and chemical properties. 

Purification. — The most important general means used 
for separation and purification are, treatment with solvents, 
crystallization, and distillation. The solvents most fre- 
quently used are water, alcohol, ether, ligroin or gasoline, 
chloroform, carbon bisulphide, benzene, glacial acetic acid, 
formic acid, amyl alcohol, acetic ether, acetone, and nitro- 
benzene. It is noticeable that all of these except water are 
carbon compounds. Alcohol is, perhaps, the most generally 
applicable. 

Crystallization may be effected by the cooling of liquid 
substances, in which case the portion that does not solidify 
is sucked away, removed by appropriate solvents, or ab- 
sorbed by spreading the solid substance on porous porcelain ; 
or, from solution, by cooling hot solutions, by evaporation or 

9 



IO ORGANIC CHEMISTRY. 

by dilution, — as, for instance, alcohol with water or ether 
with benzene. It is generally true that in the formation of 
crystals, molecules of the same kind tend to unite to form 
larger aggregates, and, in so doing, exclude molecules of 
a different kind. This tendency is not, however, universal, 
and isomorphous substances cannot be separated by crys- 
tallization. 

Crystalline Form. — The form assumed in crystallization 
is one of the most important characteristics of chemical 
compounds, and for the purpose of establishing the identity 
or non-identity of two substances the determination of the 
exact crystalline form by measuring the angles between the 
faces of the crystals has been found very important. The 
melting point of crystalline * substances is also a very definite 
and useful characteristic. When a sufficient amount of the 
substance is available, this is best determined by melting it 
in a test-tube or beaker and allowing it to cool slowly till it 
solidifies, stirring constantly with a thermometer. The 
temperature remains constant for a time at the melting 
point. It is frequently necessary to start the solidification 
by the addition of a fragment of the solid because of the 
phenomena of " overcooling." (See Ostwald, Zeit. f. phys. 
Ch. 22, 289.) 

For practical purposes, the determination of the melting 
point with the use of a minute quantity of the substance 
is usually sufficient. For this purpose a glass tube 4 or 
5 mm. in external diameter is drawn out to form alter- 
nate bulbs and capillary tubes as shown in Fig. 1. The 
narrow portion is about 1 mm. in diameter, the tubes 
are sealed off near each bulb, and for use the bulbs are 
broken in two, after scratching with a file. The finely 

* Amorphous substances do not, usually, have a definite melting point. 



CORRECTION FOR THERMOMETER. 



II 



powdered dry substance is put into the tube and shaken to 
the bottom. The tube is then attached to the thermometer by 
means of a platinum wire (Fig. 2), and heated 
slowly in a bath of concentrated sulphuric 
acid, in*a 75 cc. round bottomed flask, or, for 
substances melting above 280 , in a beaker 
containing paraffin. A greater accuracy than 
about 0.5 is not to be expected by this method. 




Fig. 



Fig. 2. 



Fig. 3. 

Correction for Thermometer. — If the stem of the thermom- 
eter is not immersed to the point of reading, the following 
correction must be added : 

JV(t—t r ) 0.000154. 

JV = number of degrees on that part of the stem of the 

thermometer outside the bath. 
/ = temperature read. 
t' = average temperature of stem. 
0.000154 = coefficient of apparent expansion of mercury 

in glass. 



12 ORGANIC CHEMISTRY. 

Impure substances, when, as is usually the case, the 
impurity dissolves in the melted substance, melt at a lower 
temperature than pure ones. Also, since the concentration 
of the solution of the impurity in the melted substance will 
usually decrease as more of the latter becomes liquid, impure 
substances will often show a range of several degrees 
between the beginning and end of melting. For the same 
reason the point of complete liquefaction is likely to be 
nearer to the true melting point than the point at which 
melting begins. A greater range than i° between the two 
points is always to be regarded with suspicion, for substances 
which do not decompose on melting. 

Very few general statements can be made about the 
melting points of organic compounds. In general, the 
experienced chemist knows that compounds of certain 
classes are usually liquids while those of other classes are 
solids at ordinary temperature, but there are so many excep- 
tions that few general statements can be made. Perhaps 
the most important general statement of this sort is that, in 
a given class of substances, compounds of symmetrical 
structure are likely to have a higher melting point than 
others which are less symmetrical. 

Distillation. — After crystallization, the most important 
means for obtaining pure substances is by distillation. Mix- 
tures usually have a different boiling point from that of their 
constituents. Since, in general, the boiling point of a mix- 
ture rises from the beginning to the end of its distillation, 
and this rise in the boiling point must correspond to a 
change in the composition of the mixture, it follows that, by 
collecting the distillate in several portions, and subjecting 
these portions to repeated distillation, a more or less com- 
plete separation of the constituents can be effected. Such a 
process is called fractional distillation. 



FRACTIONAL DISTILLATION. I 3 

Fractional Distillation. — The solution of a non-volatile 
substance in a volatile one causes a lowering of the vapor 
pressure and so a rise in the boiling point of the solvent 
(see p. 34). If both substances are volatile, the vapor pres- 
sures of the two are 'added, but at the same time each sub- 
stance tends to cause a lowering of the vapor pressure of 
the other. According as one or the other of these factors 
produces a greater effect the boiling point may be higher or 
lower than that of either constituent. We may distinguish, 
therefore, the following practical cases in the application 
of fractional distillation to the separation of two sub- 
stances : 

I. The boiling point of all 7?iixtures is higher than that of 
the lower boiling constituent and lower than that of the higher 
boiling one. In such a case a practically complete separa- 
tion of the two constituents can be effected by repeated 
fractionation. Ethyl alcohol and water are usually given as 
an illustration of this case, but, for the reasons given below 
it is apparent that the mixture really belongs under II. It 
would seem that in the majority of cases mixtures of organic 
liquids either fall under this case, or that the minimum boil- 
ing point is reached for a mixture containing so small a 
percentage of the higher boiling constituent that the com- 
pound with lower boiling point can be obtained in a practi- 
cally pure condition. 

II. The addition of a small amount of either substance lowers 
the boiling point of the other. Since from a mixture of ethyl 
alcohol and water containing but one per cent of water the 
portion distilling first contains more water than that which 
distills later, and since from mixtures containing only a small 
per cent of alcohol, the alcohol is all found in the earlier 
portions of the distillate, a mixture of the two substances 
must come under this head. From a dilute alcohol the 



14 ORGANIC CHEMISTRY. 

mixture may be concentrated by fractioning till an alcohol 
of 96 per cent is obtained. This concentration corresponds 
to the minimum boiling point and maximum vapor pressure 
which can be obtained for any mixture of alcohol and 
water. (J. Am. Chem. Soc, 23, 463.) 

III. The addition of a small amount of either substance 
raises the boiling point of the other. If water is added to 
formic acid or if formic acid is added to water, the boiling 
point of either is raised and the vapor pressure is lowered 
till a mixture containing 77.5 per cent of formic acid and 
boiling at 107.1 is reached. In such cases the concentra- 
tion corresponding to the maximum boiling point varies 
somewhat with the pressure. (Roscoe, Ann. d. Chem. (Liebig) 
125, 320.) Substances which undergo considerable ioniza- 
tion in aqueous solution appear to afford the most marked 
illustrations of this case. 

IV. Addition of the higher boiling substa7ice lowers the boil- 
ing point of the lower boiling substance, and additio?i of the 
lower boiling substance raises the boiling point of the higher 
boiling substance. This case has not, apparently, been met in 
practice. 

The accompanying diagram will be of service in gaining a 
clear conception of the phenomena discussed. The ordi- 
nates represent boiling points, while the absicae represent 
percentages of the substance whose boiling point is found 
where the curve cuts the ordinate at the extreme right. 

The student will find it to his advantage to answer, with the aid 
of the diagram, the following questions: 

By continued fractioning, how far can the following mixtures be 
separated : 25 per cent alcohol ? 99 per cent alcohol? 50 per cent 
formic acid ? 90 per cent formic acid ? 

To which cases do solutions of hydrochloric acid and of am- 
monia belong? 



FRACTIONAL DIS TILL A TION. 



15 



An inspection of the boiling point curve will usually 
indicate the ease or difficulty with which two substances 
can be separated by fractional distillation. Thus, for ethyl 
alcohol and water, a glance at the curve shows that water 
may be easily separated from a small amount of alcohol 
and that the concentration of the alcohol to forty or fifty 



110 

Formic 
Acid 

ioi°ioo 

^ 90 

'0 

^ 80 

Alcohol 

78°3 

hC 70 

f§ 60 

50 

40 
Ether 
34.° 6 
30 


Per-eent Composition 
) 10 20 30 40 50 60 70 80 90 100_ 










































Water 

100° 

90 

Benzene 
80.° 1 

70 
60 
50 
40 
30 


















































V 


N 








































/ 






























































































































































</ 




































/ 


/ 


/ 




































/ 


/ 




















■? 




























































































































































































































































































00 90 80 70 60 50 40 30 20 10 C 



Fig. 3a. 



per cent may be easily effected, but that beyond this point 
the further concentration is increasingly difficult. In such 
cases, separation by means of repeated distillation with a 
flask or plain distilling bulb and condenser (Fig. 4) often 
becomes very tedious. The rate of separation can be greatly 
hastened by the use of various forms of apparatus which have 
been devised to secure a continuous fractional condensation 



\6 



ORGANIC CHEMISTRY. 



during the process of distillation. The most efficient appa- 
ratus of "this sort is that used in the distillation of ethyl 




Fig. 4 . 

alcohol (p. 131). Of the forms of laboratory apparatus used 
for the same purpose, Ladenburg's distilling bulb (Fig. 5) 
and Hempel's column of glass beads 
(Fig. 6) may be mentioned. 

Distillation Under Diminished Pres- 
sure. — Many substances cannot be 
distilled in the ordinary manner be- 
cause they decompose at a tempera- 
ture below their boiling point. Some 
of these can be successfully distilled 
if the boiling point is lowered by re- 
ducing the pressure. A reduction of 
the pressure to 30 mm. will usually 
cause a lowering of the boiling point 
by about 1 oo° ; the amount being gen- 
erally greater for high boiling than for low boiling substances. 
(See G. W. A. Kahlbaum, Zeit. phys. Chem. 26, 577.) A fur- 




Fig. 5. 



STEAM DISTILLATION. 



17 




ther reduction of the pressure causes an additional rapid low- 
ering of the boiling point, so that some substances may be 
distilled with advantage under the low pressures which can 
be obtained with a mercury pump. (Krafft, 
Ber. d. chem. Ges. 28, 2583 ; 29, 13 16, 2240.) 
For most purposes, however, the pressure 
is reduced by means of a good filter pump, 
and the simple apparatus shown in Fig. 7 
can be used. The tube by the side of the 
thermometer is drawn out to a very fine 
capillary, and reaches to the bottom of the 
bulb to introduce a rapid stream of small 
bubbles of air. This prevents overheating 
and bumping of the liquid, which are, 
otherwise, very troublesome. The bulb is 
usually heated in an oil bath. 

Steam Distillation. — Distillation in a cur- 
rent of steam is closely related, in principle, 
to distillation under diminished pressure. 
Substances which boil below 2 5o°-3oo° have 
a sufficiently high vapor pressure at ioo°, 
so that, if they are kept at that temperature 
in a constantly changing atmosphere, they 
will slowly evaporate. If steam is used to 
furnish the changing atmosphere, they will, 
of course, condense again along with the 
steam (Fig. 8). The rates of distillation 
will vary directly as the vapor pressure and 
directly as the molecular weight. (Why ?) It must be re- 
membered, however, that the ionization caused by the water, 
or the presence of other high boiling substances, will often 
seriously lower the vapor pressure of the substance distilled. 



Fig. 6. 



ORGANIC CHEMISTRY. 



The method is especially useful in the separation of sub- 
stances from non-volatile tarry matters. 

Boiling Point. — By boiling point is always meant, unless 
otherwise specified, the temperature at which the substance 

boils under normal at- 
mospheric pressure, 
or, in other words, the 
temperature at which 
the vapor pressure of 
the substance is the 
same as the pressure 
of 760 mm. of mer- 
cury. If the boiling 
point is determined at 
any pressure not far 
from 760 mm., the 
true boiling point may 
be closely approxi- 
correction of o.i° for each 2.7 mm. 



To Pump 




mated by applying a 
difference of pressure. 



If the thread of the thermometer is 




Fig. 8. 



ANALYSIS. 19 

not entirely immersed in the vapor, the same correction must 
be applied as for melting points (p. 11). 

Many relations have been discovered between the boiling 
points of various carbon compounds. The most important 
of these is, that for .substances of similar structure an increase 
in the molecular weight is always accompanied by a rise of 
the boiling point. 

Analysis. — Having obtained a substance in a state of 
purity the next step in its study must consist in its analysis. 
The qualitative examination is usually simple, as but few ele- 
ments are commonly met with, especially in substances of 
natural origin. Carbon is usually detected by the blackening 
which occurs on suddenly heating to a high temperature. 
There are a few exceptions. Hydrogen may be found by the 
formation of water when the substance is heated with dry 
copper oxide. Nitrogen may be found by heating with soda- 
lime which sometimes, but by no means always, converts it 
into ammonia ; or by heating with sodium which converts it 
into sodium cyanide. Chlorine, bromine and iodine may be 
found by burning the substance with quicklime in a tube of 
hard glass, by heating it with sodium, or by oxidizing it in a 
sealed glass tube with a small amount of fuming nitric acid, 
and silver nitrate, at a temperature of 200 to 300 (Carius). 
Sulphur may be found by heating the substances with 
sodium, which causes the formation of sodium sulphide. 
This may be detected by the blackening of a silver coin by 
the solution. 

Quantitative Analysis. — Carbon and hydrogen are deter- 
mined by burning the substance in a tube of hard glass, in a 
current of oxygen. The vapors are passed over a red-hot 
layer of dry copper oxide to complete their combustion. If 
nitrogen is present in the compound, a roll of copper gauze 



20 



ORGANIC CHEMISTRY, 



is inserted to reduce the oxides of nitrogen formed. If sul- 
phur or halogens are present, lead chromate or silver foil 
must be used to retain them. The water formed is absorbed 




Fig. 9. 

in a tube containing calcium chloride, or concentrated sul- 
phuric acid, the carbon dioxide, in bulbs containing a strong 
solution of potassium hydroxide and having attached a small 
tube filled with solid caustic potash to retain moisture 
( Fi g- 9>- 

Nitrogen. — Three methods are in general use for the 
determination of nitrogen. The absolute method, which is uni- 
versally applicable, consists in burning the substance with 
copper oxide either in the vacuum produced by a Sprengel 
pump, or in an atmosphere of carbon dioxide, and in meas- 
uring the nitrogen, after the absorption of the carbon dioxide. 
The soda-lime method, which is more limited in its applications, 
but which is accurate for amines, amides, and a large pro- 
portion of the natural organic compounds, consists in burn- 
ing the substance by heating it with a mixture of slaked lime 
and sodium hydroxide or sodium carbonate (Johnson, Am. 
Chem. /.., i, 77). The nitrogen is converted into ammonia, 
and the latter is absorbed in a measured quantity of standard 
acid. The Kjeldahl method, which, in some of its forms, is 



HALOGENS AND SULPHUR. 21 

almost universally applicable, consists in heating the sub- 
stance with concentrated sulphuric acid and potassium sul- 
phate, copper sulphate or other substances, according to its 
nature. 

Halogens and Sulphur. — The halogens are determined by- 
use of quicklime, or of fuming nitric acid as outlined above 
under qualitative examination. Sulphur is determined as 
barium sulphate after oxidation with fuming nitric acid in a 
sealed tube (Carius), or with potassium hydroxide and potas- 
sium nitrate in a silver crucible (Liebig). Oxygen is almost 
invariably determined by subtracting the percentages of 
other constituents from ioo. 

Problem. — 0.1938 gram of a substance gave 0.2600 g.C0 2 and 
0.0750 g. H2O. 0.2548 gram of the same substance gave 55.9 cc. 
N at 1 3 and 746 mm. What is the percentage composition of 
the substance? 

Empirical Formulae. — After the percentage composition 
of a substance has been determined, the simplest empirical 
formula can be deduced by an application of the following 
principle : The amount of each element present must be 
proportional to the product of the atomic weight of the ele- 
ment multiplied by the number of its atoms in one molecule 
of the compound. Thus for sodium acetate, NaC 2 H 3 2 , the 
percentages of sodium, carbon, hydrogen, and oxygen in the 
compound must be in the same ratio to each other as 
the numbers 23:24:3:32. If the percentage of each ele- 
ment is divided by the atomic weight of the element, the re- 
sulting quotients must be proportional simply to the number 
of atoms for each element. Thus, for sodium acetate : 



Sodium 


28.05 


Per cent -f 23 = 1.22 


Carbon 


29.27 


" ~ 12 - 2.44 


Hydrogen 


3.66 


" -f 1 - 3.66 


Oxygen 


39.02 


" -i- 16 = 2.44 



2 2 ORGANIC CHEMISTRY. 

In this case a mere inspection of the quotients shows them 
to be in the ratio 1:2:3:2, and the simplest empirical 
formula, NaC 2 H 3 2 , follows at once. Sometimes the sim- 
plest ratio corresponding to the quotients is not so easily- 
perceived and, in such a case, each quotient may be divided 
again by the smallest of the quotients. From the new quo- 
tients it is usually easy to derive the formula. After the 
formula has been found it is best to confirm it by calculating 
from it the theoretical percentage composition and com- 
paring this with the results found by analysis. An exact 
agreement is not, of course, to be expected, but the limits of 
the differences which should arise from errors of analysis 
are pretty well understood. Usually carbon determinations 
come out a little too low, hydrogen determinations too high, 
and nitrogen determinations, by the absolute method, too 
high. 

What is the simplest formula for the substance whose analysis 
is given on p. 21 ? 

Determination of Molecular Weight. — Analysis alone will 
not decide between an empirical formula and any multiple 
of that formula. The percentage composition of a com- 
pound of the formula Na 2 C 4 H 6 4 would be exactly the same 
as that of sodium acetate, NaC 2 H 3 2 . The decision between 
formulae which are related to each other in this way must 
be made by means of a determination of the molecular 
weight. The methods most often used for this purpose are, 
a determination of the vapor density, a determination of the 
lowering of the freezing point, or of the vapor pressure, or 
the raising of the boiling point of some compound when a 
known weight of the substance is dissolved in it, or a deter- 
mination of the composition of some simple derivative, espe- 
cially of some substitution product. 



DUMAS' METHOD. 



23 



Determination of the Vapor Density. — One gram-molecule 
(32 grams) of oxygen occupies, at o° and 760 mm., 22.39 

liters [ = — - — ). In accordance with Avogadro's hypothesis 

\ 1.429/ 
the same " normal vqlume " of any other gas under standard 

conditions must also contain one gram molecule of that gas. 
In other words, if we determine the weight in grams of 
22.39 liters of any gaseous substance under standard condi- 
tions, the result must also express its molecular weight. 

The determination may be made either by weighing a 
known volume of the vapor or by measuring the volume of 
a known weight of the vapor. 

Dumas' Method. — In Dumas' method a light glass bulb, 
having a capacity of 100—200 cc. and with the neck 
drawn out to a fine tube, is carefully weighed and a 
moderate quantity of the substance to be examined (6-10 




Fig. 




Fig. 11. 



grams) is introduced. The bulb is then placed in an ap- 
paratus where it can be surrounded with live steam, or, in 
the case of high boiling liquids, in an oil bath or some 
arrangement for heating the bulb to some constant tempera- 



24 ORGANIC CHEMISTRY. 

ture which is at least 2o°-3o° above the boiling point of 
the substance. The temperature must, of course, be noted. 
As the substance boils it expels the air in the bulb, leaving 
the latter full of the vapor. The end of the vaporization 
can be easily determined by burning the vapors as they 
escape. The tube is then sealed with a small flame and the 
bulb is cooled, cleaned, and weighed. The gain in weight 
plus the weight of air which the bulb would contain at the 
temperature and pressure of the second weighing, gives the 
weight of the vapor. The volume of the bulb is determined 
by breaking off the tip under water, and weighing the bulb 
again after it is filled. The calculations are most easily 
made by reducing the volume of the air from the temperature 
and pressure of the second weighing of the bulb, and that 
of the vapor from the temperature and pressure at the seal- 
ing of the bulb, to the volume which they would occupy at 
o° and 760 mm. The weight of a cubic centimeter of air 
may be taken as 0.001293 grams. 

Problem. — What is the weight of the normal volume and the 
molecular weight of a substance which gave the following data? 



Weight of bulb full of air . . . 

" " " " " vapor . . 

Temperature at sealing . . . . 

Barometric pressure 

Temperature at second weighing 
Weight of bulb full of water . . 



60.2572 grams. 
60.7122 grams. 
150°. 
740 mm. 

22°. 

170.26 grams. 



Determinations of molecular weight are usually made to 
decide between quantities which are quite widely different, 
and a high degree of accuracy is not required. Corrections 
for the expansion of the glass and for the deviation of the 
weight of a cubic centimeter of water from one gram are 
unnecessary. As the deviation of a vapor from the condi- 



VICTOR MEYER'S METHOD. 



25 



tion of a theoretically perfect gas is in the direction of greater 
density, the tendency is toward high results. 





Victor Meyer's Method. — Dumas' method requires a rela- 
tively large amount of material, and the presence of a small 
amount of some higher boiling impurity may 
cause a considerable error. For these reasons, 
and because of its great simplicity, the air dis- 
placement method of V. Meyer has come into 
almost exclusive practical use. A bulb hav- 
ing a capacity of about 200 
cc, and having attached to 
it a long tube, with a side 
tube near the top, is heated 
to a constant temperature by 
the vapor of some sub- 
stance * (Fig. 12). When 
air no longer escapes from 
the side tube a eudiometer 
filled with water is placed 
over the latter and the sub- 
stance, previously weighed 
in a small bottle or bulb, is 
introduced by raising the 
stopper for a moment, and 
instantly replacing it after 
dropping the bottle in, or, better, by means of the drop- 
ping arrangement shown in Fig. 13. A little glass wool 
is put in the bottom of the bulb to prevent its being broken 
by the fall of the bottle. The substance soon vaporizes, and 

* Toluene, in°, xylene, 140 , naphthalene, 218 , diphenyl amine, 3 io°, sulphur, 448°, 
phosphorus pentasulphide, 530°, or other substances, may be used according to the 
boiling point of the substance under examination. 



Fig. 13. 



Fig. 12. 



26 ORGANIC CHEMISTRY. 

the vapor expels its own volume of air, which is collected in 
the eudiometer and measured. Since the volume of the 
latter depends on the temperature at which it is measured, 
and not on the temperature at which vaporization takes 
place, the exact temperature of the bulb is unimportant. 
This has rendered the method useful for inorganic sub- 
stances at very high temperatures as well as for common 
laboratory use for organic compounds. 

Problem. — Calculate what molecular weight corresponds to 
the following results : 

Weight of substance 0.0550 gram. 

Volume of air 18.3 cc. 

Temperature 20 . 

Barometric pressure 745 mm. 

Aqueous vapor pressure (from table) . 17.4 mm. 

Hofmann's Method (Ber. d. chetn. Ges. i, 198) is especially 
useful for substances which decompose at their boiling point 
or slightly above. The substance is introduced into a barom- 
eter tube filled with mercury and surrounded with a jacket 
through which steam, or the vapor of aniline or some other 
substance, is passed. By this means the substance is vapor- 
ized under diminished pressure. 

Determination of Molecular Weights by the Lowering 
of the Freezing Point of a Solution. 

It has been found that by precipitating copper ferro- 
cyanide in the walls of a cylinder of porous porcelain, a 
gelatinous membrane is formed that will allow water to pass 
slowly through, but which is impervious to sugar and similar 
substances that are dissolved in the water. If a solution of 
sugar is placed within such a cylinder and the cylinder is 
closed with a stopper bearing a small bent glass tube, closed 
at the end, and partly filled with mercury and partly with air, 



HOFMANN'S METHOD. 



27 



and the whole is placed in a vessel containing pure water, 
water will enter through the semipermeable membrane until 
a very considerable pressure 
is developed within the cylin- 
der. This pressure is known 
as osmotic pressure, and can 
be measured by the decrease 
in the volume of air in the 
bent tube (Fig. 14). When 
this pressure has reached its 
maximum, it is approximately 
equal to the pressure which 
would be exerted if the sub- 
stance in solution occupied 
the same space in the form 
of a gas at the same tempera- 
ture. Now, if the weight, 
volume, pressure, and tem- 
perature of a gas are known, 
the molecular weight is easily 
calculated. The determina- 
tion of the osmotic pressure 
of a solution of known con- 
centration would, therefore, 
furnish the same means for 
the determination of the 
molecular weight of a sub- 
stance as the determination 
of its vapor density. Such 
a method is especially desir- 
able because many sub- Fi s- I4 - 

stances cannot be vaporized without decomposition. 

Practically, determinations of osmotic pressure are too 




28 ORGANIC CHEMISTRY. 

difficult for common use. It has been demonstrated, how- 
ever, that a mathematical relation exists between the lower- 
ing of the freezing point of a solvent and the osmotic 
pressure. (Van't Hoff, Zeit. phys. Chem. i, 481 ; Ostwald, 
Lehrbuch allgem. Chem. 1, 760.) 

If we let 

C = the lowering of the freezing point of the solvent caused 

by a gram molecular weight* of a substance in 100 

grams of the solvent, 
L = the latent heat of fusion of a gram of the solvent, in 

calories, 
T= the absolute temperature of the melting point of the 

solvent, 

then it has been shown that 

2 T 2 
C 



100 L 



when no ionization or molecular aggregation of the substance 
dissolved takes place. The values for C are approximately 
correct only for solutions which are moderately dilute. Since 
the depression of the freezing point varies directly with the 
amount of the dissolved substance in a given quantity of the 
solvent, it follows from the definition of C as given above, 
that 

MX d 

in which 

M ■=■ the molecular weight of the dissolved substance. 
^ = the weight of the substance in 1 00 grams of the sol- 
vent 
d — the observed depression of the freezing point. 

* For example, 46 grams of alcohol, C 2 H g O, or 342 grams of cane sugar, C^H^On. 



HOFM ANN'S METHOD. * 29 

Since 





s- IOOS 




* S' 7 


if 


s = weight of substance. 




S' =§» weight of solvent, 


we may write 






_ M x d x S' 
C — 1 



or M — 



100 s 
C X 100 s 



dxS' 



These equations are in convenient form for practical use. 
The first may be used for the determination, empirically, of 
the value of C for a given solvent, by using some substance 
of known molecular weight. The second is used in de- 
termining unknown molecular weights. In an empirical 
form, this method of determining molecular weights was 
developed by Raoult before the relation to osmotic pres- 
sure was pointed out by van't Hoff. 

The values of C for the solvents commonly used are : 

Water 18.S 

Benzene 49. ° 

Phenol 75. 

Formic acid 27. 7 

Acetic acid 38.8 

Nitrobenzene 707 

The determinations are usually made with Beckmann's 
apparatus as shown in the figure. The side-neck tube is 
weighed to about 0.0 1 gram; about 15 cc. of the solvent 
are introduced, and the tube is weighed again. The ther- 
mometer is graduated to hundredths of a degree, and has a 
reservoir at the top containing mercury so that it can be set 



30 



ORGANIC CHEMISTRY. 



for use at any desired temperature. It should be so set that 
the freezing point of the solvent will come near the top of 
the scale. The thermometer and stirrer are then placed in 
the solvent, and the whole is placed 
in the glass tube, which serves 
as an air-jacket. This is sur- 
rounded with water or some liquid, 
which should be at a temperature 
of about 5 below the freezing point 
of the solvent. The solvent is 
slowly stirred, and the temperature 
allowed to fall slowly till the sol- 
vent begins to freeze. The tem- 
perature will always fall below the 
freezing point and will then rise as 
the ice separates. The thermom- 
eter should be tapped gently with 
a lead pencil as the temperature 
rises, and the highest point reached 
is taken as the freezing point. The 
temperature should not fall more 
than o.2° to 0.3 below the freezing 
point of the solvent. The starting 
of the formation of ice may be 
aided by adding some pieces of 
platinum foil and, in extreme cases, 
by introducing a minute fragment 
of the frozen solvent. 

Correction for Overcooling. — A 

correction for overcooling may also 

be applied. The ice which sepa- 

Fig. 15. rates consists of the pure solvent, 




CORRECTION FOR OVERCOOLING. 3 I 

and its separation causes an increase in the concentration 
in proportion to the amount of ice which separates. In 
the case of water, since the latent heat for the melting 
of ice is 80 calories, an overcooling of i° will cause the 
separation of -fa of the weight of the solvent in the form 
of ice. The concentration of the solution will be in- 
creased gL and the depression observed will be increased 
in the same proportion. Of course, overcooling of the pure 
solvent causes no change of concentration and introduces no 
error. On this basis, the corrections which must be sub- 
tracted from the observed depression for each degree of 
overcooling are as follows. 

Water 1.25 per cent. 

Benzene 0.96 " " 

Formic acid 0.87 " " 

Acetic acid 1.02 " " 

To apply this correction, the lowest point reached by the 
thermometer must, of course, be observed. Each determina- 
tion of the freezing point should be repeated two or three 
times, and successive observations should agree within two 
or three thousandths of a degree. 

After the melting point of the pure solvent has been 
determined a weighed portion of the substance to be 
examined is added, and the determination repeated. An 
amount should be taken which will cause a depression of 
o.3°-o.5°. This will be 0.12 to 0.20 gram for 15 grams of 
acetic acid and a substance having a molecular weight of 
100. After determining the freezing point, a second and 
third portion of the substance may be added and the 
determinations repeated. 

In using formic or acetic acid, especially, great care must 
be taken to avoid the admission of moisture, best by passing 



32 ORGANIC CHEMISTRY. 

a current of dry air through the upper portion of the side- 
neck tube. 

While the molecular weights, as determined by the freez- 
ing-point method, usually approximate closely to the true 
values, there are many cases in which the results do not agree 
with those determined by means of the vapor density. Thus 
alcohols and organic acids often give, in benzene, values for 
the molecular weight which are about twice too great, prob- 
ably because of a molecular aggregation in these compounds. 
In water, on the other hand, strong acids and salts give 
values which are much too low, because of ionization. 

Molecular aggregation appears to occur much less fre- 
quently in acetic acid than in some of the other solvents. 
It is, therefore, the most suitable solvent for general use. 

Determination of Molecular Weights by Rise in the 
Boiling Point of Solutions. 

The connection between the vapor pressure and osmotic 
pressure of a solution may be derived as follows : — 

Suppose the cylinder, in the figure, to be filled with a solu- 
tion and closed below by a semipermeable membrane. Sup- 
pose it to be immersed below in the pure solvent, and that 
the height of the column of liquid in the cylinder is such as 
to exactly balance the osmotic pressure. Suppose, also, that 
the whole is surrounded by an atmosphere consisting only 
of the vapor of the solvent. Under these circumstances, the 
vapor pressure of the pure solvent must be greater than the 
vapor pressure of the solution by exactly the pressure caused 
by the weight of a column of vapor of the same height 
as the column of liquid which balances the osmotic pres- 
sure ; for if the difference in vapor pressure were less than 
this, the pure solvent would vaporize and the vapor would 
condense in the solution ; or, if the difference in vapor pres- 



DETERMINATION OF MOLECULAR WEIGHTS. 



33 




sure were greater than the pressure of the column of vapor, 
the vapor would condense below, and some of the solvent 
would vaporize from the solution above. 
Either result would cause a change in 
the height of the column of liquid, and 
this would be followed by the passage 
of the solvent through the semiperme- 
able membrane ; and the same process 
would be repeated indefinitely. In 
other words, we should have a per- 
petual motion set up in the system in 
spite of the friction in the membrane 
and on the walls of the cylinder. Such 
a conclusion is contrary to all experi- 
ence, as expressed in the law of the 
conservation of energy. We must con- 
clude, therefore, that the forces in the 
system are in equilibrium, and that the 
difference in vapor pressure between the solvent and solu- 
tion is as stated. 



V:-- ■-■= ^~-~--. 



Fig. 16. 



Problem. — What is the height of the column of benzene vapor 
which corresponds to the difference in vapor pressure for the fol- 
lowing data, assuming that the benzene vapor has the normal den- 
sity corresponding to its molecular weight and the mean vapor 
pressure ? What is the pressure exerted by a column of the solu- 
tion of the same height, expressed in millimeters of mercury? 
What is the molecular weight of ethyl benzoate calculated from 
the osmotic pressure, volume of the solution, temperature of the 
experiment, and weight of ethyl benzoate present? 



Weight of benzene (C G H,.) ioo. grams. 

" ethyl benzoate (C 6 H 5 C0 2 C 2 H 5 ) . . . 2.47 " 

Vapor pressure of pure benzene at 8o° 751.86 mm. 

" " " solution " " 742.60 " 

Sp. gr. of solution at 8o° 0.815 



34 ORGANIC CHEMISTRY. 

Sp.gr. of mercury 13.59 

1 cc. of the benzene vapor weighs 

78.* 747 273 _ , 

— x ~~ x — — gram. — 0.00265 gram. 

22390 760 353 

(Nernst, Theoretische Chemie, p. 124.) 

Practically, an accurate determination of vapor pressures 
has been found too difficult for common laboratory use. 
Since, however, for small changes in vapor pressure the dif- 
ferences in vapor pressure are directly proportional to the 
differences in boiling point, a determination of the rise in 
the boiling point of the solution will answer the same pur- 
pose as a determination of the lowering of the vapor pres- 
sure. The formula for calculating the results is the same 
used in case of the lowering of the freezing point, viz. : 

100 x C X s 

r X S 

M = Molecular weight. 

2 T 2 t 
C = Constant = • 

100X 

j- = Weight of substance. 
S f = Weight of solvent. 
r — Rise in boiling point. 

The values for C are : 

C Boiling Point. 

Ethyl ether 21.1 34-9° 

Carbon bisulphide 23.7 46. ° 

Acetone 16.7 56. 3 

Chloroform 36.6 61. 2 

Ethyl alcohol 11.5 78.3 

Benzene 26.7 80.4 

Water 5.2 ioo.° 

* The molecular weight in grams divided by the normal volume in cubic centimeters, 
t In this 7' is the absolute temperature of the boiling point, and L the latent heat of 
vaporization. 



DETERMINATION OF MOLECULAR WEIGHTS. 



35 



Acetic acid 25.3 118. 

Ethylene bromide 63.2 131.6 

Aniline . - 32.2 i^3-7° 

Of the various forms of apparatus devised for making the 
determination, one qf the simplest is that devised by H. C. 
Jones (Fig. 17). The vessel in which the boiling point is 
determined is about 18 cm. high 
and 4 cm. in diameter at the lower 
part. It is filled to a depth of 3 
or 4 cm. with glass beads. The 
thermometer bulb is surrounded 
with a cylinder made by rolling up 
a piece of platinum foil to prevent 
radiation. Some pieces of plati- 
num foil f cm. square, with corners 
bent alternately up and down and 
edges serrated, are put inside of 
the cylinder to secure even boiling. 
The glass cylinder is closely 
wrapped with asbestos paper to a 
height of 12 cm., and the whole 
placed on a thick piece of asbestos 
cardboard having a hole 3^ cm. 
in diameter in the center. On this 
opening is placed a piece of fine 
copper gauze, with which the glass 
is brought in contact. The con- 
nections for the thermometer and 
condenser must be with sound cork 
stoppers. The top of the con- 
denser may be closed with a cal- 
cium chloride tube to advantage. 

In making the determination the 




apparatus is weighed, 



36 



ORGANIC CHEMISTRY. 



the solvent is introduced and weighed, and the boiling point 
determined. The thermometer must be tapped occasionally 
with a lead pencil, and vigorous, regular boiling must be se- 
cured. The barometer should be read, and any change of 

pressure during the determina- 
tion must be taken into ac- 
count. A known weight of the 
substance is then introduced, 
either through the condenser, 
or, with high boiling solvents, 
through the side tube, and the 
determination of the boiling 
point is repeated. A correc- 
tion, estimated at from 0.2 to 
0.4 grams, according to the 
form of the apparatus and na- 
ture of the solvent, may be 
subtracted from the weight of 
the solvent because of the 
amount of the latter in the 
condenser and on the walls of 
Fi s- l8 - the apparatus. 

The low-boiling solvents, as ether and benzene, appear to 
be most satisfactory for general use. 

Recently several forms of apparatus have been devised, 
in which the solution is boiled by the vapor of the solvent 
and overheating is avoided. One of the best of these is 
that of McCoy (Am. Chan. J. 23, 353) shown in Fig. 
18. The volume of the solution is measured, instead of 
weighing it. The molecular weight is calculated by the 
formula, — 

WT 




M = 



AF 



DETERMINATION OF MOLECULAR WEIGHTS. 37 

W = weight of substance in grams. 

T= a constant. 

A = the rise of the boiling point. 

V= the volume of the solution in cubic centimeters. 

The values of T fof common solvents are : 

Alcohol 1560 Carbon bisulphide . 1940 

Ether 3030 Acetone 2220 

Chloroform .... 2600 Aniline 3820 

Benzene 3280 Water 540 

Determination of Molecular Weights by Means of Substitution 
Products. — If one or more atoms of a compound can be re- 
placed by an atom or group of atoms, a comparison of the 
composition of the original substance with that of its substi- 
tution product will often decide as to the minimum possible 
molecular weight. Thus the simplest formula which agrees 
with the composition of acetic acid is CH 2 0. The composi- 
tion of sodium acetate (p. 21) cannot, however, be reconciled 
with any simpler formula than Na C 2 H 3 2 . 

As no salt of acetic acid can be found in which a larger 
proportion of hydrogen has been replaced, the formula of 
the acid must be C 2 H 4 2 , or some multiple of that. 

Problem. — A hydrocarbon has the composition: 

Carbon 92.31 per cent. 

Hydrogen 7.69 per cent. 

The simplest bromine substitution product of the hydrocarbon 
contains 50.96 per cent of bromine. What is the formula of the 
hydrocarbon ? 

For the determination of the molecular weights of acids 
the silver salts are often used, for bases the chlorplatinates 
( R 2 PtCl 6 ) are usually suitable, and for hydrocarbons the 
halogen substitution products. 



38 ORGANIC CHEMISTRY. 

The following principles are also occasionally useful in de- 
ciding between possible formulas. Only one hydrocarbon 
containing an odd number of hydrogen atoms is now known. 
( Triphenylmethyl, Gomberg,/". Am. Chem. Soc. 22, 757.) Also, 
only one compound is known in which the sum of the num- 
bers of atoms of odd valence (H, CI, Br, I, N, P, Na, etc.) is 
not an even number. These facts are, of course, connected 
with the fact that, as far as known, the valence of carbon is, 
with the single exception, always four or two. 

Laboratory Exercises. 

1. Determination of the melting point of urea, paranitrotoluene, 
succinic acid, salicylic acid, parahydroxybenzoic acid. 

2. Fractional distillation of a mixture of alcohol and water ; of 
10 parts of benzene with 90 parts of alcohol and of 10 parts of al- 
cohol with 90 parts of benzene, followed by a determination of the 
per cent of benzene in the first and last fractions of each case by 
precipitation with water ; of a dilute hydrochloric acid and of a 
concentrated hydrochloric acid, with a determination of the specific 
gravity of the residual fraction ; of the light oil from coal-tar. 

3. Determination of carbon and hydrogen in cane sugar and in 
benzene. 

4. Determination of carbon, hydrogen, and nitrogen in urea, 
uric acid, and paranitrotoluene ; calculation of formulas. 

5. Determination of bromine in bibrombenzene. 

6. Determination of sulphur in sulphanilic acid. 

7. Determination of silver in silver acetate. 

8. Determination of water of crystallization and of calcium in 
calcium succinate. 

9. Determination of the molecular weights of ether, chloroform, 
and benzene by Dumas'. and by V. Meyer's methods. 

10. Determination of the molecular weights of benzoic acid 
and of nitrobenzene in glacial acetic acid, by the freezing-point 
method. 

11. Determination of the molecular weight of benzoic acid in 
benzene by the boiling-point method. 



SPECIFIC GRAVITY. 



39 



'CHAPTER II. 
PHYSICAL PROPERTIES. 

In addition to melting point and boiling point, several 
other physical properties of organic compounds are of im- 
portance in their study, partly for purposes of identification, 
partly because relations have been discovered between some 
of these physical properties and the structure of some com- 
pounds. While these physical properties have, thus far, 
been very rarely useful in deciding questions of doubtful 
structure, it is altogether probable that some of them will 
prove increasingly valuable, for that purpose, in the future. 

Specific Gravity. Molecular Volume. — Determinations of 
specific gravity with the hydrometer are only approximate 
unless spindles having a very 
small range and a slender stem 
are used. The Westphal bal- 
ance (Fig. 19), if care is taken 
to have the liquid at the 
proper temperature, is rapid, 
and accurate to the third or 
fourth decimal place. The in- 
strument should be carefully 
tested with pure water. 

For greater accuracy, or for 
use with a small quantity of substance, some form of pycno- 
meter is practically most useful. The form with a ther- 




Fig. 19. 



4Q 



ORGANIC CHEMISTRY. 



mometer (Fig. 20) is very accurate when a sufficient quantity 
of material is available. A smaller form is useful for small 
quantities of material. The capacity may be from one to 
two cubic centimeters, and the neck, where the mark is 
placed, should be drawn down to an 
internal diameter of about one milli- 
meter. The pycnometer may be easily 
filled, emptied, or dried by means of a 
pipette drawn out to a not too fine capil- 
lary. After filling, and allowing to stand 
in a bath of the proper temperature for ten 
minutes, the liquid above the mark may be 
removed by means of narrow slips of filter 
paper. 

Specific gravities are referred either to 
water at the same temperature, or at 4 . 

2 0° 

Thus the symbol D —5- is used to indicate 




Fig. 20. 



the density of the substance at 20 as com- 
pared with water at 4 . If the specific 
gravity referred to water at 20 has been found, that referred 
to water at 4 may be calculated by subtracting 0.00174 for 
a substance having a specific gravity of one or a propor- 
tional amount for other specific gravities. The correction 
for other temperatures may be taken from tables giving the 
density of water. 

Molecular Volume. — By molecular volume * is meant the 
volume in cubic centimeters occupied by a gram molecular 
weight of the substance, that is, by the number of grams 
corresponding to its molecular weight. It is found by 
dividing the molecular weight by the density. Thus the 



* The term specific volume was formerly used for this quantity. 



MOLECULAR VOLUME. 4 1 

density of ethyl -alcohol, C 2 H 6 0, at its boiling point, is 

0.7381 c. Its molecular volume is — = 62.32. 

16 b 0.73815 6 

A very large amount of work has been done for the pur- 
pose of collecting material on which to base an intelligent 
discussion of the relation between the composition of organic 
compounds and their molecular volumes. Kopp, who was 
the pioneer in this field {Ann. d. Chem. (Liebig), 41, 79 
(1842); 96, 153, 303 (1855); 250, 1, (1889), introduced the 
method of comparing molecular volumes at the boiling 
points of the compounds, and that method has been generally 
followed by others. In 1855 Kopp formulated the following 
general rules : 

1. A difference of CH 2 causes a difference of 22 in the 
molecular volume. 

The molecular volume of acetic acid, C 2 H 4 Q 2 is 63.6 

The molecular volume of propionic acid, C 3 H 6 2 is 85.5 

Difference 21.9 

2. One atom of carbon can be replaced by two atoms of 
hydrogen without changing the molecular volume. 

The molecular volume of ethyl benzoate, C 6 H 5 C0 2 C 2 H 5 is 
173.6. 

That of ethyl valerianate, C 4 H 9 C0 2 C 2 H 5 is 173-6. 

That of amyl acetate, CH 3 C0 2 C 5 H n is 174.4. 

These rules were based on a considerable number of 
determinations from which the illustrations given have been 
selected. From these results Kopp drew the conclusion 
that the atomic volume of carbon is 1 1 and that of hydrogen 
5.5 giving a total of 22 for the group CH 2 . He also assigned 
the value of 12.2 as the atomic volume of carbonyl oxygen 
(in the group C = 0) and 7.8 as that of hydroxy 1 oxygen. 
Values were also given for the atomic volumes of chlorine, 



42 ORGANIC CHEMISTRY. 

bromine, iodine, nitrogen and sulphur. The values given 
later by Lossen for these elements are CI = 22.8, Br. = 29.1, 
I = 39.6, S = 23.5, N = 7, CN = 30, N0 2 = 32.6. 

A careful examination of the large amount of material 
which has now been accumulated, leads to the conclusion 
that molecular volumes calculated on the assumption of a 
constant atomic volume for each element are, in many cases, 
only approximate. Molecular volumes are, evidently, de- 
pendent, in part, on the structure of the compound, on the 
number of atoms in the molecule and on other factors, and 
it has not, hitherto, been possible to give to all of these 
factors a general, accurate, mathematical expression. 

The following general statements are of interest. Some 
of them may possibly have a greater significance than is now 
understood. Double or triple unions (as in carbonyl, C = 0, 
in unsaturated carbon compounds and probably in cyanogen, 
C = N) increase the molecular volume. The formation of 
a ring, on the other hand, causes a decrease in the molecu- 
lar volume. Thus the molecular volume of cyclopentane, 

CH 2 -CH 2 

>CH 2 , is 93.2 at 20. 5 while that of 2-methyl-2- 

CH 2 - CH 2 

butene, CH 3 -CH = C-CH 3 , is 106.8, although the empirical 

I 
CH 3 

formula of each is the same. The double union in one com- 
pound and the ring structure in the other are evidently 
connected with the large difference in molecular volumes. 

Isomeric compounds, even when having similar structure, 
often have different molecular volumes. Thus the molecular 

CH 2 C1 
volume of ethylene chloride, | at its boiling point, 84. i°, 

CH 2 C1 
is 85.2, while that of ethylidene chloride at 57.7 , is 88.2. 



VISCOSITY. 



43 



In such cases the substance with the lower boiling point 
has, almost invariably, the greater molecular volume. 



Surface Tension or Capillarity. — Comparatively few gen- 
eral relations have been found between the surface ten- 
sion of organic liquids and their 
structure or composition. Deter- 
minations of the coefficient of sur- 
face tension have, however, given 
a means of determining the de- 
gree of molecular aggregation of 
liquids. (Ramsay and Shields, 
J. Chem. Soc. 63, 1089 (1893). ) 

Practically, determinations of 
capillarity have proved useful for 
the determination of the strength 
of alcohol and of the amount of 
fusel oil in alcohol. For this pur- 
pose the determination is made 
either by determining the height 
to which the liquid will rise in a 
small tube or the number of drops 
given by a fixed volume of the 
liquid. An instrument used for 
the latter purposes is called a 
stalagmometer. (Traube, Ber. d. 
chem. Ges. 20, 2644, 2824.) 




Fig. 21. 



Viscosity. — Determinations of 
viscosity are usually made by de- 
termining the time required for a given volume of the 
liquid to pass through a capillary tube under a given differ- 
ence of pressure. Such determinations are, thus far, of 



44 ORGANIC CHEMISTRY. 

little theoretical interest, but are practically valuable in the 
study of machine oils. Another method of determination is 
founded on the resistance to a cylinder rotating in the oil. 
(Doolittle's Viscosimeter (Fig. 21), /. Amer. Chem. Soc. 15, 

I73-) 

Critical Temperature. — This constant is most simply de- 
termined by heating the liquid in a sealed glass tube, in an 
air-bath, till the temperature is reached at which the bound- 
ary between liquid and vapor disappears. (Knietsch, Ann. 
Chem. (Liebig), 259, 116; Altschul, Zeit. phys. Ch. 11, 581; 
16, 26.) Apart from its theoretical interest, the determina- 
tion is of value in judging of the purity of a substance. 

Specific Heat, Heat of Vaporization and Heat of Melting. — 

Determinations of these constants have proved, thus far, of 
little theoretical value in organic chemistry, except as con- 
nected with the lowering of the freezing point and the vapor 
pressure of solutions (pp. 26-37). 

Heat of Combustion. — By heat of combustion is meant the 
heat, in calories, developed by burning one gram molecule of 
the substance to carbon dioxide and liquid water. It is most 
easily and accurately determined, for most substances, by 
burning in an autoclave in an atmosphere of compressed 
oxygen, the autoclave being surrounded with a known weight 
of water, the temperature of which is accurately taken before 
and after the combustion (Berthelot). The following are the 
most important general laws which have been established : — 

In any homologous series the addition of a CH 2 group, in 
a?i ope?i chain, increases the heat of combustion by about 
158,000 gram-calories, or 158 Cal. 

The heat of combustion of compounds containing only 
single unions between carbon atoms is less than that of com- 



HEAT OF FORMATION, 45 

pounds of the, same composition containing double unions. 
Thus the heat of combustion of cyclohexane, 



CHg-LHg-CHt 



is less than that of hexene, CH 3 CH 2 CH 2 CH 2 CH = CH 2 . 
This indicates that 'carbon atoms which are doubly united 
are not more firmly but, rather, less firmly held than those 
between which there is only a single union. Triple unions 
still further increase the heat of combustion. 

Isomeric compounds of similar structure have very trifling 
differences, if any, in their heats of combustion. 

Heat of Formation. — By heat of formation is meant the 
heat which would be developed on the combination of the 
elements to form one gram molecule of the substance. It is 
calculated by subtracting the heat of combustion of the sub- 
stance from the heat of combustion of the elements of which 
it is composed. 

By this method of calculation the heat of formation of 
some substances, as, for instance, that of acetylene, is nega- 
tive. This can be satisfactorily explained only by assuming 
that carbon is combined with itself in amorphous carbon 
and that hydrogen is combined with itself in gaseous hy- 
drogen. 

Rationally, heat of formation would mean the heat re- 
sulting from the combination of the elements when in the 
free atomic state. In this sense, heat of formation cannot, 
at present, be experimentally determined, and all methods of 
calculation thus far proposed are dependent on uncertain 
hypotheses.* 

* For the sake of uniformity, the values for heats of combustion given in this book 
are taken, as far as possible, from the tables of Stohmann (Zeit.fiir phys. Ch. 6, 334 
and 10, 410). In calculating heats of formation Stohmann assumes the heat of com- 
bustion of 12 grams of carbon as 94 Cal. and that of 2 grams of hydrogen as 69 Cal. 



46 ORGANIC CHEMISTRY. 

Molecular Refraction. — By molecular refraction is meant 
the constant calculated by the formula : 

M(n 2 - i) 
(;/ 2 + 2) / " 
M = Molecular weight. 
n = Index of refraction (ratio of the sine of the angle of 
incidence to the sine of the angle of refraction, or 
ratio of the velocity of light in air to that in the 
substance). 
$ == Density or specific gravity. 

The molecular refraction of compounds, for the red hydro- 
gen line, may be calculated by means of the following "re- 
fraction equivalents " of the elements. (Briihl, Zeit. fihys. 
C/i. 7, 191.) 

C = 2.365 

H = 1. 103 

O in OH = 1.506 

O in C-O-C = 1.655 

O in C = O = 2.328 

N (as NC) = 2.76 

CI = 6.014 

Br = 8.863 

I == 13.808 

Thus the molecular refraction of acetic acid calculated by 
means of these constants is : 



'or C 2 


2.365 


X 


2 = 


4-73° 


" H 4 


1. 103 


X 


4 = 


4.412 


" -0- 






= 


1.506 


" =0 






= 


2.328 
[2.976 



The actual determination gives the value 12.93. 



CIRCULAR POLARIZATION. 47 

The presence of a double union between carbon atoms 
increases the molecular refraction by 1.836, that of a triple 
union increases it by 2.22. This relation between refractive 
power and structure has sometimes proved useful in the 
study of compounds o'f unknown structure. 

The index of refraction is determined by use of a hollow 
glass prism or by means of Pulfrich's refractometer. (See 
Ostwald, Handbuch filr physikalisch-chemische Messimgen, p. 
170, or Walker's translation, p. 142.) The latter instrument, 
which depends on a determination of the angle of total re~ 
flection, is especially useful because only a very small quan- 
tity of the substance is required. 

Molecular Dispersion. — This is calculated by the formula : 

(n* + 2) d ~ (« 2 + 2)d ' 

M is the molecular weight and n and n x are the indices 
of refraction for two different lines of the spectrum. The 
dispersive as well as the refractive power is very considera- 
bly increased by the presence of double unions between 
carbon atoms. 

Color. — A very large proportion of the carbon compounds 
are colorless, or, in powdered condition, white. Certain 
pretty well defined classes of compounds, and especially cer- 
tain classes of nitrogen compounds, are brilliantly colored, 
however. Such compounds usually show, also, charac- 
teristic absorption spectra. 

Circular Polarization. — If a tube containing certain or- 
ganic substances is placed in the path of a ray of polarized 
light, the plane of polarization will be rotated through a defi- 
nite angle, dependent on the nature of the substance, length 



4 8 



ORGANIC CHEMISTRY. 



of the tube, temperature, color of the light and nature of the 
solvent, if a solvent is used. The angle of rotation is deter- 
mined by means of instruments called polarimeters or sac- 




Fig. 22. 

charimeters, according to their use and construction, the 
determination being frequently made for the commercial 
valuation of sugars. The specific rotation, [a], is calculated 
by the formula : 

M = ~ 



Ipd 



a = the observed angle of rotation, 
/ = the length of the column of liquid in decimeters, 
p = the per cent of the substance present by weight, 
d = the density of the solution. 



ELECTRICAL CONDUCTIVITY. 49 

It is sometimes convenient to substitute for pd the number 
of grams of the substance in 100 cc. of the solution. The 
specific rotation may be determined either for white light or 
for the sodium or some other light. If the sodium light is 
used, it is written [a]^. If white light is used, [a]y . 

The relation between rotatory power and structure will be 
considered later. 

Magnetic Molecular Rotation. — This has been defined by 
the formula, 

rM 

i\M x d 

r = the observed rotation in a given magnetic field, 
M = the molecular weight of the substance, 

d = the density of the substance, 

r x = the rotation caused by water in the same field, 
Af t = the molecular weight of water =18. 

In some cases there appears to be a connection between 
the magnetic rotation and the constitution of carbon com- 
pounds. (W. H. Perkin, Sen., J. Chevi. Soc, 45, 421; 53, 561; 
59, 9 8l 

Electrical Conductivity. — The measurement of the elec- 
trical conductivity of those organic compounds which disso- 
ciate in aqueous solutions, that is, of acids, bases, and salts, 
has given many results of value, and new applications of 
such determinations to the study of important problems are 
given every year. 

The "specific resistance " of solutions * is usually taken as 
the resistance offered by a cube whose edge is 1 cm. The 

* The " specific resistance " is also sometimes defined as the resistance offered by a 
prism of i mm. cross section and x meter in length. As so defined it is io.ooo times 
greater than as defined in the text. 



50 



ORGANIC CHEMISTRY. 



" specific conductivity " is the reciprocal of the " specific 
resistance." The "molecular conductivity," fx, is defined as 
the product of the volume of the solution, in cubic centi- 
meters, which contains one gram molecule of the substance, 
multiplied by the specific conductivity of the solution. 

Thus the specific conductivity of a -^ normal solution of 

potassium chloride is 2.244 X 
io -3 at 18 * or 2.594 X io~ 3 
at 2 5 . Since a -^ normal solu- 
tion contains one gram molecule 
in 50,000 cc, the molecular con- 
ductivity : 

At i8°= 2.244 X io _3 x 50,000 

= 112. 2, 
At 25°= 2.594 x io~ 3 x 50,000 

= 129.7. 

The determination of the 
absolute conductivity of a solu- 
tion is attended with very con- 
siderable difficulty. Instead of 
this the determinations are usu- 
ally made with a cell of the 
form shown in the figure. Two 
circular electrodes, 3 or 4 cm. 
in diameter, are attached with 
gold solder, or by welding, to 
stout platinum wires, which are 
then sealed into the ends of glass tubes which may be filled 
with mercury for convenient electrical connection. The con- 

* In Siemens's mercury units, which are usually employed in work of this kind. 
For conversion of conductivity into reciprocal ohms, see Kohlrausch and Holborn, Leit- 
vermogen der Elektrolyte, 1898. 




Fig. 23. 



ELECTRICAL CONDUCTIVITY. 



51 



ductivity of some solution whose molecular conductivity is 
known (for example, that of a -£$ normal solution of potas- 
sium chloride) is first determined with the cell; the latter 
is then filled with the solution to be studied, and the meas- 
urement repeated, and, by comparison, the molecular con- 
ductivity of the solution can be easily calculated. 

The measurements of resistance can be understood from 
the following diagram : 




Fig. 24. 

C is the cell whose conductivity is to be determined ; R is 
a box of resistance coils ; AB is a wire of uniform size, best 
of platinum or manganine (an alloy containing manganese) ; 
D is a sliding contact ; I is an induction coil of high pitch, 
giving the necessary alternating current, as a direct current 
cannot be used because of polarization ; T is a telephone. 
If the contact D is shifted till no sound is heard in the tele- 
phone, that is, till a current no longer passes between D and 
E, the resistance of the cell, r, will be to the resistance R, 
as b : a, or 



r = R 



or C 



R X b 

in which C is the conductivity of the solution in the cell, and 
a and b are the distances AD and BD. If we let c stand 
for the specific conductivity of the solution used, then the 
constant, k, of the cell may be defined as 

c c X R X b a 

£ = — = , or c = k — • 

C a R X b 



52 ORGANIC CHEMISTRY. 

Having determined this constant, the specific conductivity 
of any other solution in the same cell will be 

c'=k 



R'Kb' 



And since the molecular conductivity is equal to the vol- 
ume, z>, occupied by one gram molecule multiplied by the 
specific conductivity (see above), the molecular conduc- 
tivity is, 

Preparatory to use the electrodes are covered with plati- 
num black by electrolyzing a dilute solution of chlorplatinic 
acid in the cell. During the measurements the cell is kept 
at a constant temperature (usually 25 ) in a thermostat. 
The water used for the solutions must be carefully purified, 
and especially must be free from carbonic acid and ammonia. 

The conductivity of a solution of an electrolyte depends 
on two factors, — first on the velocities of the ions of which 
it is composed, and second, on the degree of dissociation of 
its molecules into ions. 

At an infinite dilution the dissociation is complete, and at 
any other concentration the percentage dissociation, a, can 
be calculated by the formula, 

a = — • 

flco 

The value of fx v is determined as indicated above. The 
value of [x<* for acids is determined by means of the molec- 
ular conductivity of their sodium salts. The velocity of the 
hydrogen ion is u = 325 at 25 , that of the sodium ion is 
u = 49.2. If therefore 325 — 49.2 = 275.8 is added to the 
conductivity of the sodium salt at infinite dilution, \x.*> for 



ELECTRICAL CONDUCTIVITY. 53 

the acid is obtained. Since the sodium salts undergo a 
high degree of dissociation at moderate dilutions, and since 
the departure of the conductivity of the sodium salts from 
their maximum values is nearly the same for all acids, the 
following factors may be added instead of the one given 
above, when the molecular conductivity of the salt has been 
determined, v is the volume in liters occupied by one gram 
molecule of the salt. 

V = 32 64 128 256 512 I024 OO 

^ = 287.8 285.8 283.8 281.8 279.8 277.8 275.8 

For most complex acids the following empirical values 
may also be used : 

For acids containing 12 atoms /n x= 358 



15 


' Mcc=356 


18 


' P«= 354 


22 


' M*=352 


2 5 


" V*=35 l 


30 


" m*=35° 



For bases /xoo + 1 may be determined in a similar manner 
to the above, with the use of the nitrate. 

In accordance with Ostwald's law of dilution, 

2 

= constant = k. 



(1 — a) v 

In this formula a is the percentage dissociation, and v is 
the volume in liters occupied by one gram molecule of the 
acid, base, or salt. It is evident that for substances which 
are highly dissociated at a moderate dilution k will be large, 
and vice versa, k becomes, therefore, the most convenient 
measure of the degree of dissociation, or, as it is usually 
stated, of the strength of acids or bases. The value of this 
factor is a highly characteristic property of individual acids 



54 ORGANIC CHEMISTRY. 

and bases, and will be often referred to in the following 
pages. For organic acids and bases a constant K (= i oo k), 
one hundred times greater than that given above, is usually 
employed. (Ostwald, Zeit. phys. Ch. 3, 174.) 

Laboratory Exercises. 

1. Determination of the specific gravity of kerosene with a 
hydrometer, with a Westphal balance, and with a pycnometer. 

2. Determination of the viscosity of samples of machine oil. 

3. Determination of the heat of combustion of naphthalene and 
of camphor in a bomb calorimeter ; calculation of the heat of 
formation. 

4. Determination of the molecular refraction of benzene. 

5. Determination of [a] D and [a] . for cane sugar in an aque- 
ous solution. 

6. Determination of K for acetic acid, chloracetic acid and 
benzoic acid. 

7. Determination of the basicity of succinic and benzoic acids 
(Ostwald, Handbuch fiir fthy siko-chemische Messungen, p. 281, or 
Walker's translation, p. 235). 



HYDROCARBONS. 55 



CHAPTER III. 
HYDROCARBONS. MARSH-GAS SERIES. 

In an important sense the hydrocarbons, or compounds of 
carbon and hydrogen, are looked upon as the fundamental 
compounds of organic chemistry from which all other com- 
pounds are derived. This is partly because very few car- 
bon compounds, comparatively speaking, are known which 
do not contain hydrogen ; partly because it is practically 
convenient to consider carbon compounds as substitution 
products of the hydrocarbons, that is, as substances in which 
other elements or groups of elements have taken the place of 
hydrogen atoms in the hydrocarbons. 

As regards their empirical formulae, all of the hydro- 
carbons may be classified in groups or " series," in each of 
which the number of hydrogen atoms bears a fixed mathe- 
matical relation to the number of carbon atoms. 

In the first or limiting series (Ger., Grenzkohlenwasser- 
stoffe) the general formula is C re H 2w+2 , the successive mem- 
bers having the formulae, CH 4 , C 2 H 6 , C 3 H 8 , etc. This is 
known as the marsh-gas series from its first member. 

Members of the second series have the general formula, 
C w H 2n ; of the third series, C n H 2w _ 2 . Members of each 
successive series up to that having the general formula, 
C n H 2n _ 40 , are known. One hydrocarbon of the series, 
C w H 2n _ 54 , is also known. 



56 ORGANIC CHEMISTRY. 

Marsh-Gas Series, or Paraffins, C w H ; 







Boiling Melting 


Specific 






Point. Point. 


Gravity. 


CH 4 


Methane 


-152° -186 


0.415 at 


-164° 


C 2 H G 


Ethane 


- 90° 







C 3 H 


Propane 


- 37° 


■ 




C 4 H 10 


Butane 


+ i° 


0.60 


(o°) 




Methylpropane 


- n-5° 







C 5 H 12 


Pentane 


36° 


o-6337 


(i5°) 




Methylbutane 


3i° 


0.6271 


(i5°) 




Dimethylpropane 


9 ° - 20° 







C 6 H 14 


Hexane 


69 


0.6654 


(*5°) 




2 Methylpentane 


62° 


0.6766 


(o°) 




3 Methylpentane 


64° 


0.6765 


(20.5 ) 




2, 3 Dimethylbutane 


53° 


0.6680 


(i7-5°) 




2, 2 Dimethylbutane 


49.6° 


0.6488 


(20°) 


C 7 H 16 


Heptane 


984° 


0.6885 


(i5°) 




2 Methylhexane 


90.3° 


0.7067 


(o°) 




3 Methylhexane 


9i° 


0.6895 


(20°) 




3 Ethylpentane 


95°-98° 


0.689 


(2 7°) 




3, 3 Dimethylpentane 


86°-87° 


0.7111 


(o°) 


C 8 H 18 


Octane 


125-5° 


0.7188 


(o°) 




2, 5 Dimethylhexane 


108.5 


0.6975 


(i5°) 


C y H 20 


Nonane 


i49-5° . -5i° 


0.7217 


(i5°) 




2,6 Dimethylheptane 


132° 


0.7247 


(o°) 


C 10 H 22 


Decane 


i73° -3o° 


0.7342 


(i5°) 




2 Methylnonane 


i 5 o -i6o° 









2, 7 Dimethyloctane 


s ^0° 


o-7358 


(9-8°) 




3, 6 Dimethyloctane 


i59°-i62° 


0.7463 


(22°) 



The normal hydrocarbons (p. 66) of the series are known, 
and are named, logically, from the Greek numerals, up to 
tetracosane, C 24 H 50 . A few of still higher molecular weight 
are known, the highest having the formula C 60 H 122 . 

Homology. — A consideration of the general formula for 
the series shows that it is dependent on the valence of carbon 
and that of hydrogen. In a molecule containing two carbon 



HOMOLOGY. 57 

atoms one valence, or power of combination,* of each car- 
bon atom must be used to hold the molecule together, and 
but three valences of each atom will be available for combi- 
nation with hydrogen atoms. With three carbon atoms two 
valences of one carbbn atom must be used in holding to the 
other two, and one valence of each of the other atoms must 
be employed in a similar manner, leaving but eight of the 
twelve valences of the three carbon atoms available for 
combination with hydrogen. The bearing of these state- 
ments as applied to the successive members of the series will 
be more apparent from the following graphical formulae : 

H 

I 
Methane H — C — H 

I 
H 

H H 

I I 
Ethane H - C - C - H 

H H H 

I I I 

Propane H-C-C-C-H 

I I I 

H H H 

It is apparent that the successive members differ from 
each other by the group CH 2 , and that the addition of one 
carbon atom renders possible the addition of two hydrogen 
atoms. This relation is characteristic of all other series of 
hydrocarbons as well as of the paraffins, and is known as 

* Sometimes called bonds or linkages. The terms valence, or power of combination, 
are, perhaps, less definite, and correspond better to our very imperfect knowledge of 
the forces within the molecule. 



58 ORGANIC CHEMISTRY. 

homology. The series are called homologous series, and any 
hydrocarbon or compound is said to be a homologue of hydro- 
carbons or compounds in the same series containing a differ- 
ent number of carbon atoms. 

Methane or Marsh-gas, CH 4 . — This is the only hydrocar- 
bon known containing but one atom of carbon in the mole- 
cule. It is formed in nature by the decomposition of 
vegetable matter covered with water, and comes to the sur- 
face in an impure form when the decaying organic matter on 
the bottom of a shallow pool of water is stirred with a pole. 
This gave rise to the name marsh-gas. The gas appears 
to be formed by the action of micro-organisms, and it has 
been demonstrated in the laboratory that filter paper (cellu- 
lose, (C 6 H 10 O 5 ) n , will decompose in the presence of water, 
under the influence of the micro-organisms found in sewage 
with the formation of methane. 

The methane given off from the seams of coal, and known 
as fire-damp, has, very probably, a similar origin. Methane 
has also been found easting under high pressure in the 
pores of rocks covered wifh an impervious layer of shale or 
similar material. When a hole is bored into such a rock the 
gas escapes ; and it has proved of great economic value in 
Pennsylvania, Ohio, Indiana and elsewhere under the name 
of natural gas. The gas usually contains some nitrogen and 
larger or smaller quantities of ethane, or other homologues, 
and of hydrogen sulphide. It has never been found to con- 
tain hydrogen. Natural gas has also been long known in 
the Caucasus, giving rise there to the sacred fires of the 
Parsees. 

The origin of natural gas is still uncertain. The most 
probable theory about it would seem to be that it has been 
formed by the decomposition of vegetable or animal matter 



METHANE OR MARSH-GAS. 59 

in a manner similar to that by which the gas of the marshes 
is produced. 

Another theory (MendelejefFs) is that it is formed by the 
action of water on metallic carbides. This theory has re- 
ceived some support recently by the discovery that aluminum 
carbide is decomposed by water with the formation of 
methane (Moissan). 

A1 4 C 3 + 12 H 2 = 3 CH 4 + 4 Al (OH) 8 . 

Methane is formed when almost any form of organic mat- 
ter is heated to a high temperature, and so forms a consider- 
able proportion of coal gas and of oil gas. It is also formed 
in small amounts when hydrogen is brought in contact with 
heated carbon, and, hence, is found in very small amount 
in water-gas. 

Marsh-gas may be obtained by passing a mixture of car- 
bon bisulphide and hydrogen sulphide over heated copper. 

CS 2 + 2 H 2 S + 8Cu = CH 4 + 4 Cu 2 S. 

These methods of preparation are not practically useful, 
but they are interesting because, theoretically, they may be 
made the starting point for the preparation of nearly all of 
the other hydrocarbons and other compounds of the series, 
and indeed, of other series as well. They form a part of 
the evidence which has demonstrated that there is no real 
difference between " organic " and " inorganic " compounds. 

Methane is most easily prepared by heating a mixture of 
dry, fused sodium acetate with four times its weight of soda- 
lime, in a tube or retort of hard glass. 



CH 3 ] C0 2 Na + NaO ] H = CH 4 + Na 2 C0 3 . 



60 ORGANIC CHEMISTRY. 

Pure methane may also be prepared by dropping a mix- 
ture of alcohol, methyl iodide, and a drop of sulphuric acid, 
on a copper-zinc couple. The couple can be prepared by 
heating gently a mixture of copper powder with three parts 
of powdered zinc and allowing it to cool in a closed flask. 

CH 3 I + H 2 = CH 4 + HI or 
2 CH 8 I + 2 Zn + 2 H 2 == 2 CH 4 + Znl 2 + Zn (OH) 2 . 

These methods are, both of them, general, and may be 
used for the preparation of a great number of hydrocarbons, 
of this and of other series. 

Methane is a colorless, tasteless gas. It is the lightest 
compound gas known. What is its density ? 

It may be condensed to a liquid by high pressure, but only 
at low temperatures, its critical temperature being — 7 6°. 
Under atmospheric pressure it boils at about — 152 . It 
solidifies at — 18 6°. 

In its chemical properties methane is very stable. Its 
kindling temperature (67 o°) is higher than that of hydrogen 
(650 ) or of amorphous carbon (375-500 ). This is one rea- 
son for the efficiency of the Davy safety lamp, and is a cause 
of some difficulty in the use of natural gas in gas engines, 
and in the explosion of mixtures of methane and air in gas 
analysis. 

Mixtures of chlorine and methane explode violently in 
direct sunlight. In diffused daylight, the action is more 
gentle, and substitution products are formed. 

CH 4 + Cl 2 = CH 3 C1 + HC1. 

Methyl chloride. 

If the substitution is carried to its limit, carbon tetrachlo- 
ride, CC1 4 , is formed, but the reaction has not been practi- 
cally useful because of the difficulty of confining it to the 
formation of a single product. 



ETHANE. 6 1 

Ethane. — C 2 H C . This may be prepared : 

i. By treatment of ethyl iodide, C 2 H 5 I, mixed with alco- 
hol and a drop of sulphuric acid with the zinc-copper 
couple, or by warming ethyl iodide with water and zinc dust. 

2. By the electrolysis of acetic acid, CH 3 C0 2 H, or its 
salts. The anion CH 3 C0 2 which is liberated at the positive 
pole decomposes at once into carbon dioxide and methyl, 
CH 3 , and the latter combines with itself to form ethane, 
CH 3 -CH 3 . This method of preparation is of especial inter- 
est because it demonstrates the presence of two methyl 
groups in ethane, and furnishes a confirmation of the graphi- 
cal formula which has been based on theoretical reasons 
(p. 57). The presence of a methyl group in acetic acid and 
in sodium acetate is demonstrated by the preparation of 
methane from the latter. 

C 2 H 3 2 Na + NaOH = CH 4 + Na 2 C0 3 . 

It is evident from this reaction that in sodium acetate the 
three hydrogen atoms were all combined with the same 
carbon atom. 

3. By dropping water cautiously into cooled zinc ethyl. 



C 2 H B I HO|H njJ _ 

C 2 H> Zn+ HO|H = 2CA + Zn ^ 



From the methods of preparation it is evident that we 
may look upon ethane as composed of two methyl groups, or 
as composed of an ethyl (C 2 H 5 ) group and hydrogen. It is 
important to notice that the different methods of preparation 
give the same compound, and that the ethyl group must 
contain one methyl group. (Schorlemmer, A?m. d. Chem. 
(Liebig), 131, 76; 132, 234.) 



62 ORGANIC CHEMISTRY. 

The names methyl, ethyl, propyl, butyl, etc., are given to 
the groups formed by the removal of one hydrogen atom 
from the corresponding hydrocarbons. 

Ethane is a gas, but may be condensed to a liquid more 
easily than methane. The liquid boils at — 90 . In chem- 
ical properties ethane resembles methane quite closely. It 
burns with a somewhat more luminous flame, but the illumi- 
nating power is only one-half that of ethylene. 

Propane. — This may be prepared from propyl iodide, 
C 3 H 7 I, or from zinc propyl, Zn (C 3 H 7 ) 2 , by methods similar 
to those given for ethane. 

Propane condenses to a liquid at — 17 . It is very 
slowly absorbed by fuming sulphuric acid, and appears to 
be slightly more reactive than methane or ethane, but is very 
indifferent toward most chemical agents. 

Substitution Products of Propane. — When one hydrogen 
atom of propane is replaced by a halogen atom, or by some 
group of atoms, two classes of compounds may be obtained. 
An understanding of the relation between these two classes 
of compounds is necessary before the butanes can be intelli- 
gently discussed. 

When ethyl iodide, CH 3 CH 2 I, is heated with potassium 
cyanide, ethyl cyanide, CH 3 CH 2 CN, is formed. 

C 2 H 5 I + KCN = C 2 H 5 CN + KI. 

When ethyl cyanide is properly treated with sulphuric 
acid, it is decomposed with the formation of propionic acid, 
CH 3 CH 2 C0 2 H, and ammonium sulphate. 

2 CH 3 CH 2 CN + H 2 S0 4 -f- 4 H 2 

= 2 CH 3 CH 2 C0 2 H + (NH 4 ) 2 S0 4 . 

In the fusel oil which is obtained as a by-product in the 
manufacture of common alcohol there is found a small 



PROPANE. 63 

amount of normal propyl alcohol which has the empirical 
formula C 3 H 8 0. If this alcohol is oxidized by means of a 
mixture of potassium pyrochromate and dilute sulphuric acid, 
the same propionic acid which is obtained from ethyl cyanide 
is formed. 

C 3 H 8 + 20 = CH 3 CH 2 C0 2 H + H 2 0. 

On the other hand, if normal propyl alcohol is treated with 
red phosphorus and iodine, it is converted into normal 
propyl iodide, C 3 H 7 I. 

5 C 3 H 8 + 5 I + P = 5 C 3 H 7 I + H 3 P0 4 + H 2 0. 

The relations which have been sketched will be clearer 
from the following diagram : 

kcn h 2 so 4 

CH 3 CH 2 I ->- CH 3 CH 2 CN -^ CH 3 CH 2 C0 2 H 

A K 2 Cr 2 7 
T + H 2 S0 4 . 
P + I 

C 3 H 7 I -<- C 3 H 8 0. 

These relations demonstrate that normal propyl iodide 
contains the ethyl group, CH 3 CH 2 — , and that the iodine is 
combined with the end carbon atom. The only graphical 
formula consistent with these relations and with the valence 
of the atoms concerned is the following : 

H H H 

I I I 

H-C-C-C-I. 

I I I 
H H H 

When calcium acetate is heated it decomposes, and ace- 
tone distils over. 

Ca<^ 3 ° 2 =CaC0 3 + C 3 H e O. 

^2^3^2 Acetone. 



64 ORGANIC CHEMISTRY. 

If acetone is reduced by means of sodium amalgam, iso- 
propyl alcohol, C 3 H 8 0, is formed. This gives, with iodine 
and red phosphorus, isopropyl iodide, C 3 H 7 I. When either 
isopropyl alcohol or acetone is oxidized a mixture of acetic 
and formic acids is obtained. 

C 3 H 8 + 4 = C 2 H 4 2 + CH 2 2 + H 2 0. 

Acetic acid. Formic acid. 

This difference in the conduct of isopropyl alcohol as 
compared with normal propyl alcohol can be satisfactorily 
explained only by supposing that the oxygen in the former is 
combined with the central instead of the end carbon atom. 
Since the iodine of isopropyl iodide takes the place of this 
oxygen and one hydrogen atom, it follows that the iodine in 
that compound must be combined with the central carbon 
atom. This gives the graphical formulae : 

H 

I 
H O H 

I I I 

-C-C-C-H and H-C-C-C-H, 

I I I 

H H H 

for isopropyl iodide and isopropyl alcohol. 

Isomerism. — Different compounds having the same per- 
centage composition are often met with among the carbon 
compounds. Such compounds are said to be isomers. If 
isomers have the same molecular weight, as in the case just 
considered, they are called metamers. If they have differ- 
ent molecular weights, as, for instance, acetylene, C 2 H 2 , and 
benzene, C 6 H 6 , they are called polymers. 

Isomers differ, of course, in their physical or chemical 
properties, and usually in both. Thus normal propyl iodide 



H 

1 


I 


H 

1 


1 
C - 

1 


1 
C - 

1 


1 

- C 

1 


1 
H 


1 
H 


1 
H 



graphical Formulae. 65 

boils at 102. 2 , isopropyl iodide at 89. 5 . Normal propyl 
iodide has a specific gravity of 1.7557 at 15 , isopropyl iodide 
a specific gravity of 1.7 109. When isopropyl iodide is heated 
with water at ioo° in a sealed tube, isopropyl alcohol and 
hydriodic acid are formed. Undoubtedly normal propyl 
iodide would, under the same conditions, give normal propyl 
alcohol, but the experiment has not, apparently, been tried. 

Graphical Formulae. — Formulae similar to those which have 
been given for the two propyl iodides are frequently very 
useful as giving a concise expression to the knowledge 
gained about the structure of carbon compounds. It should 
be remembered that such formulae are of value and trust- 
worthy only when they are based on a careful study of the 
methods of formation and of decomposition of the compounds 
for which they are given. 

As ordinarily used, such formulae express merely the view 
which is held as to what atoms within the molecule are in 
direct combination with each other, and are not intended, 
further than that, to represent stereomeric or space relations 
within the molecule. For this reason, formulae may often be 
written which appear, at first sight, very different but which 
represent identical structures. Thus the formulae 

HI H H 

I I 11 

H-C-C-H I-C-C-H 

H I and . I H 

H-C-H H-C-H 

l l 

H H 

have the same structural significance as that already given 
for isopropyl iodide because each formula represents the 
same atoms as in direct combination with each other. 



66 ORGANIC CHEMISTRY. 

Arrangement in Space. — It has been found, it is true, that 
a considerable number of compounds cannot be satisfactorily 
understood without a more definite discussion of the arrange- 
ment of their atoms in space ; and this has given good rea- 
son for the belief that certain definite space relations must 
exist between the atoms in all compounds. This more defi- 
nite view is reserved for a later discussion. 

In most cases it is convenient to use somewhat abbre- 
viated graphical formulae. Thus isopropyl iodide is usually 

written, CH 3 -CHI-CH 3 , or ,^ TT 3 > CHI. To save space, 

CH 3 

such formulae are often used where fuller formulae would, 
perhaps, be better. Until the beginner has become thor- 
oughly familiar with their exact meaning, he will find it use- 
ful, occasionally, to expand such formulae into their full 
graphical form. 

Butanes, C 4 H 10 . — Since butane must be considered as a 
propane in which one hydrogen atom has been replaced by 
a methyl group, the discussion of the propyl iodides leads 
us to expect two isomeric butanes. This expectation is veri- 
fied by experience. 

Normal* butane, CH 3 -CH 2 -CH 2 -CH 3 , is prepared by heat- 
ing ethyl iodide with zinc, or by treating it with sodium 
amalgam. 

2 CH 3 CH 2 1 + 2 Na = CH 3 CH 2 CH 2 CH 3 + 2 Nal. 

The structure of the compound is evident from the method 
of formation. Normal butane is a gas which condenses to 
a liquid that boils at i°. 

CTT 

Isobutane, or 2-methyl propane, r ^ TT 8 > CH-CH 3 , is pre- 

CH 3 

* By "normal" is meant a hydrocarbon in which no carbon atom is combined 
directly with more than two others. 



PENTANES. 6 J 

pared by dropping tertiary butyl iodide (2-methyl-2-iodo-pro- 
pane *), , ^ 

CHg— C — CHg , 

I 

CH 3 
on zinc covered with water, or by boiling isobutyl iodide 

PTT 

(2-methyl-i-iodo-propane) 3 > CH-CH 2 I with zinc dust 
and water. 

2 C 4 H 9 I + 2 Zn + 2 H 2 O=C 4 H 10 + Znl 2 + Zn (OH) 2 . 

Isobutane boils at — n.°5-t The chemical properties of 
the butanes are similar to those of propane. They are indif- 
ferent toward most chemical agents except chlorine and bro- 
mine. Each of them gives two mono-substitution products. 
What would be the graphical formulae of the chlorbutanes ? 

Pentanes, C 5 H 12 . — If a methyl group is substituted for 
one hydrogen in each of the butanes, two pentanes will be 
obtained from each, according as the substitution takes place 
in connection with a central or an end carbon atom. An 
examination of the resulting formulae shows, however, that 
two of the pentanes obtained are structurally identical. This 
agrees with the results of experience, as but three pentanes 
have been prepared. A simpler discussion of the theoreti- 
cally possible formulae for the pentanes is based on a con- 
sideration of each hydrocarbon as a derivative of the 
hydrocarbon corresponding to the longest chain of carbon 
atoms in its molecule. It is evident that we can have but 
one pentane with a chain of five carbon atoms. This is 
normal penta,7ie. 

i CH 3 CH 2 CH 2 CH 2 CH3. 

* For nomenclature, seep. 68. t Determined by E. F. Phillips under my direction. 



-S .'C CHEMISTRY. 

With a chain of four carbon atoms, the attachment of a 
methyl group to either of the end carbon atoms would give 
a chain of five atoms: i.e.. normal pentane. An attachment 
of the group to either central carbon atom, since the^ 
symmetrically placed in the molecule, would give the same 
>r, as it was formerly called tatte. 

™ s > CH-C1L-CH,. 
L H. 

Nc other arrangement of :V e . bon atoms, giving a chain 
of four, is >ss ble. 

With a chain of three carbon atoms, the only manner by 
which two carbon atoms can be attached without giving a 
chain of four atoms is by attaching two methyl groups to the 
1 al n. This gives // 

• 

CH. , CH 
;. »> C < 

CH ? ^ CH. 

The three pentanes have been prepared by methods which 
leave no doubt as to their structure: but a discussion of the 
methods us ad is io4 n e ; e ssary here. 

I: is noticeable that throughout the seric- I ; isomer with 
has a hig her boiling point. The dif- 
ference - pecific gravity are slight, and the difficulty of 
rarity is so gi eat that no law in the matter 
can be considered as Established. 

Hex.-r.es. . H M ; Official Nomenclature. — Five hexanes are 
mssiblc :al formulae for these maybe 

i by using the principle of the longest carbon chain as 

>ame prin- 
ciple is applied in the ."■"■" ' * for the hydro- 

■ : .- m. Chem..' 



HEXANES. 69 

carbons of the series and their derivatives. In this system 
of nomenclature each compound is to be considered as a 
derivative of the hydrocarbon corresponding to the longest 
chain of carbon atoms in the compound. To indicate the 
points of attachment j:or the various side chains, or substitut- 
ing atoms, or groups, the carbon atoms are numbered, be- 
ginning at the end nearest to a side chain. 

Thus CH 3 CHCH 2 CH 2 CH 2 CH 3 

I 
CH 3 

is methyl-2-hexane. CH 2 ICH 2 CH 3 is iodo-i-propane. 

In the case of side chains containing two or more carbon 
atoms, the latter receive a second smaller number beginning 
with the one nearest the point of attachment, thus : — 

CO ( 2 ) (3) (4) (5) (6) (7) 

CH 3 - CH - CH 2 - CH - CH„ - CH 2 - CH 3 

I I 

CH^ 1 ) CH,^ 1 ) 

I 
CH 3 ( 4 2 ) 

When a hydrocarbon radical is introduced in a side chain 
it is designated by the prefixes metho-, etho-, etc., instead 
of the usual methyl, ethyl, etc. Thus : — 

CH 3 - CH 2 - CH 2 - CH - CH 2 - CH 2 - CH 3 

I 
CH 3 - CH 

I 
CH 3 Metho-ethyl-4-heptane. 

In a strict application of the official nomenclature the 
names pentane, hexane, etc., are reserved for the normal 
hydrocarbons ; i.e., for those having no side chains, or, in 
other words, for those in which no carbon atom is directly 
united to more than two others. 



JO ORGANIC CHEMISTRY. 



Higher Members of the Methane Series. 

The number of possible isomers increases very rapidly for 
hydrocarbons having a greater number of carbon atoms. 
The theory indicates the possibility of nine heptanes, C 7 H 16 , 
75 decanes, C 10 H 22 , and 802 tridecanes, C 13 H 28 . At present, 
however, only five heptanes are known, and only a compara- 
tively very small number of isomers containing a larger 
number of carbon atoms. The student will find it useful to 
develop the possible formulae for the hexanes and heptanes 
as a means of securing a better understanding of the possi- 
bilities of structural isomerism. A further discussion of the 
subject here is unnecessary. 

Many of the normal hydrocarbons of the series have been 
prepared by methods which establish their structure. 

Normal octane has been prepared from normal butyl iodide 
and sodium. 

2 CH 3 CH 2 CH 2 CH 2 I + 2Na = CH 3 (CH 2 ) 6 CH 3 + 2NaI. 

Normal decane, CH 3 (CH 2 ) 8 CH 3 , has been prepared in a 
similar manner from normal octyl bromide, ethyl iodide and 
sodium, and normal eikosane from normal decyl iodide, CH 3 
(CH 2 ) 8 CH 2 I, and sodium. 

General Properties of the Paraffins. 

The first four members of the series are gases at ordinary 
temperatures. Normal pentane boils at 3 6°, normal hexane 
at 69 , and the boiling point increases with the number of 
carbon atoms but the differences grow less. From tetrade- 
cane, C 14 Hgo, upward, the hydrocarbons are white, solid, wax- 
like bodies at temperatures above o°. The specific gravity 



PETROLEUM. ?l 

also increases more and more slowly, and is nearly constant 
at 0.78 for the higher members. 

Chemically, the paraffins are very inert, chlorine in direct 
sunlight being about the only agent which readily attacks 
them.* It has been found recently, however, that nitro- 
derivatives and sulphonic acids may be obtained by the action 
of dilute nitric acid, and of concentrated sulphuric acid on 
some of them. (Konowalow, Ber. d. chem. Ges. 28, 1852 ; 29, 
2199, Worstall, A?n. Che?)i. J. 20, 202 and 664.) 

Petroleum. — In certain limited areas in Pennsylvania, 
Ohio, Indiana, Texas, California, and Canada, on the shores 
of the Caspian Sea, and in a few other places in Europe, 
large natural reservoirs filled with a crude oil known as pe- 
troleum are found. These reservoirs are covered with an 
impervious layer of shale or other rocks which have pre- 
vented the escape of the oil. When a hole is bored through 
this impervious layer the petroleum is usually forced to the 
surface by the hydrostatic pressure of the water found below, 
and often flows in enormous quantities. After a time the flow 
decreases, and may then, usually, be increased by exploding 
a charge of nitroglycerine in the bottom of the well to break 
up and open seams in the rocks below. The composition of 
the petroleum from different sources varies considerably. 
American oils consist largely, though by no means exclu- 
sively, of hydrocarbons of the marsh-gas series. The oils 
from the Caspian Sea contain considerable quantities of cyclic 
hydrocarbons of the general formula C„H 2n . California pe- 
troleum contains considerable amounts of benzene and its 
homologues. In all cases, petroleum is a very complex mix- 
ture. Compounds of the marsh-gas series have been ob- 

* The name paraffin (meaning " with little affinity ") is given because of this inert 
character. 



J 2 ORGANIC CHEMISTRY. 

tained from it by prolonged fractional distillation, and by 
treatment with concentrated sulphuric acid and with nitric 
acid to remove members belonging to other series. The 
hydrocarbons which have been isolated in this manner have 
been identified by their boiling points, specific gravities, vapor 
densities, and especially by means of their chlorine derivatives 
and the compounds which can be prepared from these by 
simple reactions. (Schorlemmer, Proc. Roy. Soc, Vols. 14, 
15, 16, 18, 19, and 20; Warren, Am. J. Sri., Vols. 39,40,41, 
44, and 45 ; Proc. Am. Acad. Arts and Sri., 9, 177 (1867), 
Mabery, Ann. chem.J. 19, 243, 374, 419, 482, 796.) 

Caucasus petroleum. (Beilstein and Kurbatow, j5Vr. d. chem. 
Ges. 13, 1S18; 14, 1620; Markownikow, Ibid. 16, 1873; 20, 
1850; Ann. d. chem. (Liebig), 234, 89. Origin of petroleum, 
Engler, Per. d. chem. Ges. 21, 18 16 ; 22, 592; 26, 1449; 
33, 7 ; Kraemer and Spilker, Ibid. 32, 2940 ; 35, 12 12.) 

Most of the hydrocarbons which have been isolated from 
the American petroleum have been normal, but recently 2, 3- 
dimethyl butane has been found in Russian petroleum (As- 
chan), and the presence of methyl-propane in American 
petroleum seems probable (Mabery). The Ohio, Indiana, 
and Canadian petroleums contain sulphur compounds con- 
sisting in part of methyl sulphide (CH 3 ) 2 S, ethyl sulphide 
(C 2 H 5 ) 2 S and other sulphides of the aliphatic series. 
(Mabery and A. W. Smith, Am. Chem.J. 13, 233.) 

For commercial purposes petroleum is purified by subject- 
ing it at first to a crude fractional distillation, which is usually 
carried on till only a residue of coke remains in the retort. 
The high temperatures during the last part of the distillation 
cause the decomposition or " cracking " of the higher boiling 
portions, and so increase the portion of medium boiling point, 
which is most valuable. The oils are further purified by 
agitation with concentrated sulphuric acid, with a solution 



FLASHING-POIN T. 73 

of sodium hydroxide, and with water. Oils containing sul- 
phur are purified by boiling them with fine copper oxide. 
The copper sulphide formed is regenerated by roasting it in 
furnaces. Finally, the portion to be used as kerosene is dis- 
tilled with steam to remove the lower boiling portions and 
raise the " flashing-point " (see below) as high as required. 
The commercial products, in order of boiling point, are : 
Cymogene and rhigolene, used sometimes in artificial-ice 
machines. Ligroin or petroleum ether, an especially purified 
low-boiling product much used as a solvent in laboratories. 
Low-boiling gasoline which is sufficiently volatile so that air 
saturated with its vapor may be burned as an illuminating 
gas. High-boiling gasoline used in gasoline cook-stoves. 
Naphtha and benzine used for cleansing purposes, and usually 
nearly or quite identical with high-boiling gasoline. Kerosene 
of various grades, used in lamps. Paraffin oils and other 
high-boiling oils used for lubricants. Vaseline, a high-boiling, 
semisolid body used for medical purposes. Paraffin obtained 
by cooling the high-boiling portions to a low temperature, and 
separating the solid portion by means of a large filter press ; 
used for the manufacture of candles and in electrical insu- 
lation. All of these substances are, of course, complex 
mixtures from which definite compounds can be isolated only 
with great difficulty. 

Flashing-point. — The safety of kerosene depends largely on 
the absence from it of hydrocarbons which might escape in 
sufficient amount to form an explosive mixture with air. The 
presence of such hydrocarbons is determined by the flashing- 
test. In its simplest form the determination consists in pla- 
cing some of the oil in a small beaker with a thermometer 
and warming slowly till a small flame, which is brought near 
the surface of the oil at regular intervals, causes a momen- 



74 ORGANIC CHEMISTRY. 

tary flash. More reliable forms of apparatus have been 
proposed, but have not been adopted for general use. A 
minimum flashing-point of 65.5 (150 F) has been fixed by 
most of our States. 

Laboratory Exercises. 

1. Preparation of methane. 

2. Preparation of ethane. Determination of its density. 

3. Comparison of the conduct of benzine and of benzene toward 
concentrated sulphuric acid, and toward a mixture of sulphuric 
and nitric acids. 

4. Determination of the flashing-point of a sample of petroleum. 



UNSATURATED HYDROCARBONS. 



75 



CHAPTER IV. 

ETHYLENE SERIES. UNSATURATED 
HYDROCARBONS. 



Name. 

Ethene 
Propene 
i-Butene 
Cis-2-butene 



Trans-2-butene 
Methyl-propene 

i-Pentene 
2-Pentene 
2-Methyl-i-butene 

2-Methyl-2-butene 

2-Methyl-3-butene 



i-Hexene 
2-Hexene 
2-Methyl-2-pentene 



3-Methyl-3-pentene 

2.2-Di-methyl-3-butene 

2.3-Di-methyl-2-butene 



-5" 
+ i-5 c 

+ 2. 5 < 



Formula. 

CH2 ^ CH2 

CH 3 — CH ^ CH 2 

CH 2 = CH — CH 2 CH 3 

GH 3 — CH 

' II 
CH,- CH 
CH 3 — C — H 
II 
H— C — CH 3 
CH 3 -C = CH 2 —6° 

I 
CH 3 

CH 2 = CH- CH 2 — CH,- CH 3 40 

CH 3 — CH = CH — CH 2 — CH 3 36 

CH 2 = C-CH 2 — CH 3 32° 
I 

CH 3 

CH 3 — C = CH — CH 3 36.8 

CH 3 
CH 3 — CH — CH = CH 2 21.2 

CH 3 
CH 2 =CH— CH 2 — CH 2 — CH 2 — CH S 68 -70= 
CH 3 — CH=CH— CH 2 — CH 2 CH 3 6 7 ° 



Boiling Specific 
Point. Gravity. 



0.63s (i3-5 c ) 



Cxi 3 — (_• — Oxi — C/H2 ^- , -t^3 

CH 3 
CH 3 — CH 2 — C = CH — CH 3 

CH, 
CH 3 — C — CH = CH a 
/ \ 

CH, CH 3 
CH.— C=G — CH, 



66- 



0.670 
0.6783 (o°) 



0.6997 (o°) 
0.702 (o°) 



0.712 (o c ) 



0.712 (o°) 



CH 3 CH 3 



76 ORGANIC CHEMISTRY. 

Six heptenes, six octenes, and two nonenes of known 
structure have been prepared. A considerable number have 
also been obtained for which the structure is uncertain. 

Empirically, members of the second series of hydrocar- 
bons have the general formula, C n H 2M . In reality there are 
two series having this formula, the ethylene or ethene series 
and the saturated, cyclic series. 

Ethylene or Ethene, C 2 H 4 . — The first member of the series 
should be methylene, CH 2 , but all attempts to obtain such a 
compound have proved unsuccessful. A number of com- 
pounds, such as carbon monoxide, C = O, hydrocyanic acid, 
H — N = C, and others may be considered as derivatives of 
methylene, and the properties of some of these indicate that 
methylene, if momentarily formed, would prove so reactive 
as to combine at once with itself to form ethylene or some 
other polymer. 

Ethylene, C 2 H 4 , is usually prepared by mixing ethyl alco- 
hol, C 2 H 5 OH, with one and two-thirds times its volume of 
concentrated sulphuric acid and heating the mixture to about 
1 7 5°. The alcohol at first reacts with the sulphuric acid to 
form ethyl sulphuric acid, and this decomposes at the tem- 
perature given with the formation of ethylene and sulphuric 
acid, 

C 2 H 5 OH + H 2 S0 4 = C 2 H 5 HS0 4 +H 2 

Ethyl sulphuric acid. 

C 2 H 5 HS0 4 = C 2 H 4 + H 2 S0 4 . 

At a lower temperature ether, (C 2 H 5 ) 2 0, (p. 165), is formed, 
and the ethylene is always contaminated with that and other 
impurities. 

Pure ethylene may be obtained by warming an alcoholic 
solution of ethylene bromide, C 2 H 4 Br 2 , with granulated zinc. 

C 2 H 4 Br 2 + Zn = C 2 H 4 + ZnBr 2 . 



UNSATURATED COMPOUNDS, JJ 

Both methods are general and may be applied to the 
preparation of many other hydrocarbons of the series and to 
the preparation also of their derivatives from alcohols and 
hydroxyl compounds, and from bromine compounds having 
two bromine atoms combined with adjacent carbon atoms. 

Ethylene is formed when almost any carbon compound is 
subjected to destructive distillation. It is present in coal 
gas and oil gas, and is very important in giving illuminating 
power. 

Ethylene is a colorless gas with a sweetish odor. Its 
kindling temperature is 580 , very considerably below that 
of methane and ethane. In this as in many other properties, 
ethylene is less stable than members of the marsh-gas series. 

Ethylene combines directly with chlorine or bromine 
to form ethylene chloride, C 2 H 4 C1 2 , or ethylene bromide, 
C 2 H 4 Br 2 . These are colorless oils of a pleasant odor, and 
the formation of the former gave to ethylene its old name of 
olefiaiit gas. At ioo° ethylene unites directly with hydro- 
bromic or hydriodic acid to form ethyl bromide, C 2 H 5 Br, or 
ethyl iodide, C 2 H 5 I. A cold, neutral solution of potassium 
permanganate oxidizes it to ethylene glycol. 

C 2 H 4 + O + H 2 = C 2 H 4 (OH) 2 . 

Ethylene glycol. 

Unsaturated Compounds. — These reactions are all of them 
characteristic not only of ethylene but of its homologues, and 
of almost all of their derivatives, whether belonging to this 
or to other series. From this point of view, their importance 
can scarcely be overestimated. The conduct of these com- 
pounds toward the halogens and the halogen acids has given 
rise to the term unsaturated^ as applied to them, The radi- 
cal difference between their conduct and the conduct of satu- 
rated compounds of the marsh-gas series should be noticed. 

If heated to a high temperature with hydrogen, ethylene 



?8 ORGANIC CHEMISTRY. 

combines with it to form ethane ; if heated alone, methane, 
ethane, free carbon, acetylene, C 2 H 2 , benzene, C 6 H 6 , naphtha- 
lene, C 10 H 8 and many other compounds are formed. 

Structure of Ethylene. — Theoretically, three formulae 
seem to be possible for ethylene in accordance with the val- 
ence of carbon and of hydrogen. These are : 

H H H H H H 

II II II 

-C-C-, H-C-Cand C = C 

II I II 

H H H H H 

The first formula, at first thought, appears to have much 
in its favor because of the satisfactory explanation it gives 
of the " unsaturated " nature of ethylene. It represents the 
carbon atoms as practically trivalent, however, and, if carbon 
can in reality act as a trivalent element, we can see no 
reason why such groups as CH 3 , C 2 H 5 , etc., should not be 
capable of an independent existence. All reactions which 
should lead to the formation of these and similar groups 
give instead ethane, CH 3 — CH 3 , butane, C 2 H 5 — C 2 H 5 , or 
other compounds in which the two groups are united, and 
carbon shows its normal valence. In the whole list of 
hydrocarbons only one with an odd number of carbon atoms 
is known. The properties of this single compound (tri- 
phenyl-methyl, (C 6 H 5 ) 3 C) too, and especially the fact that it 
is so reactive as to combine directly with oxygen, make it 
seem very improbable that a similar condition can exist in 
ethylene. 

If the second formula represents the structure of ethylene, 
the compound, ethylene chloride, formed by the addition of 
chlorine would be i.i. di-chlorethane, CH 3 CHC1 2 , while, if 
the third formula is correct, it must be 1.2. di-chlorethane, 
CH 2 C1 — CH 2 C1. Now 1.1. dichlorethane, or as it is more 



STRUCTURE OF ETHYLENE. 79 

often called, ethylidene chloride, has been prepared by treat- 
ing acetaldehyde with phosphorus pentachloride. 



.0 
CH 3 -C( H -f-PCl 5 = 


/ CI 
= CH 3 - C - CI + P0C1 3 . 
\ H 


Acetaldehyde. 


Ethylidene Phosphorus 
chloride. oxychloride. 



The structure of acetaldehyde is deduced from the fact 
that it gives acetic acid, CH 3 -C0 2 H by oxidation, and that 
acetic acid, in turn, must contain a methyl group from the 
manner in which it gives methane (p. 59) and ethane (p. 61) 
by its decomposition. The structure of acetic acid has also 
been thoroughly established by its synthesis. 

KCN HCl 

CH 3 HS0 4 -^ CH 3 CN -^ CH 3 C0 2 H. 

Ethylidene chloride (1,1-dichlorethane) boils at 57.5° and 
has a specific gravity of 1.2044 at o°, while ethylene chloride 
boils at 83. 5 and has a specific gravity of 1.2803. Since 
only two dichlorethanes are theoretically possible, and the 
structure of ethylidine chloride is established, ethylene 
chloride, which is different, must be 1,2-dichlorethane, 
CH 2 C1CH 2 C1. Such a formula for ethylene chloride leads 
to either the first or third formula for ethylene. As the first 
has already been excluded, the formula CH 2 = CH 2 remains 
as the most probable expression for its structure. 

Double Unions. — The term " double union " gives, at first 
thought, the impression that carbon atoms which are 
" doubly united " must be held together more firmly than 
those which are singly united. Such a conclusion is com- 
pletely contradicted by the facts in the case. The point of 
double union is always one of weakness, and is usually the 
point where the compound is most easily attacked by 



80 ORGANIC CHEMISTRY. 

oxidizing agents or otherwise. On account of this, some 
authors have objected to the use of the term " double 
union." No very satisfactory equivalent for it has, how- 
ever, been proposed. 

Homologues of Ethylene. — The homologues of the series 
may be prepared by methods similar to those given for 
ethylene. They may also be formed by warming halogen 
derivatives of the marsh-gas series with an alcoholic solution 
of caustic potash. 

CH 3 CH 2 CH 2 CH 2 I + KOH = CH 3 CH 2 CH = CH 2 -f KI + H 2 0. 

Butyl iodide. i-Butene. 

Nomenclature. — In the official nomenclature the names 
correspond to the names of the methane series, the vowel a 
being replaced by e. A number is used to indicate the 
position of the double union, when necessary. The presence 
of the double union greatly increases the number of possible 
isomers. There are three butenes and five pentenes. Illus- 
trations of the use of the system of nomenclature will be 
found in the table at the beginning of this chapter. 

Physical Properties. — Members of the ethene series have 
a slightly higher boiling point than the corresponding mem- 
bers of the methane series. The specific gravity is also 
somewhat higher. The heat of combustion is less than that 
of the corresponding member of the methane series, but the 
difference is not so great as the loss of two hydrogen atoms 
would lead us to expect. 

The heats of combustion are : 

Dif. 53 Cal. (?) 
Dif. 41 Cal. 
Dif. 39.5 Cal. 



Ethane 




389 Cal. 


Ethene 




336 Cal. 


Propane 




541 Cal. 


Propene 




500 Cal. 


Dimethyl 


propane 


847.1 Cal. 


Methyl-2- 


Dutene 


807.6 Cal. 



PHYSICAL PROPERTIES. 8 1 

The combustion of two grams of hydrogen gives 68.4 Cal., 
hence the union of hydrogen with members of the ethylene 
series must be accompanied by the evolution of a consider- 
able amount of heat. 

The differences in the heats of formation (see p. 45) for 
the two series are even more significant. These are : 



Ethane 


6 Cal. 


(?) 


Propane 


17 Cal. 




Dimethyl propane 


37 Cal. 




Ethene 


— 10 Cal. 




Propene 


— 11 Cal. 




Methyl-2-butene 


— 7.4 Cal. 





The determinations on which these calculations are based 
were made by different observers, and are not all concord- 
ant, but it appears to be established beyond question that 
the heat of formation of the members of the marsh-gas series 
is always positive while that of the members of the ethylene 
series is negative. This accords with the greater stability 
of the former. 

Laboratory Exercises. 

1 Preparations of ethylene and of ethylene bromide. 

2. Compare the conduct of benzine, benzene and turpentine 
when shaken with a dilute solution of potassium permanganate. 
Turpentine is an " unsaturated " hydrocarbon, though it does not 
belong to this series. 

3. Preparation of isoamylene (2 methyl-3-butene). 



82 ORGANIC CHEMISTRY. 



CHAPTER V. 
CYCLIC HYDROCARBONS, C„H 2n . 



Cyclopropane 


CH 2 

1 >CH 2 
CH 2 




Boiling 
Point. 

-35° 


Specific 
Gravity. 


Methyl cyclopropane 


CH 2 
CH 3 — CH< | 

CH 2 




+5° 


0.6912 (20 ) 


Cyclopentane 


CH 2 — CH 2 
1 >CH 2 
CH 2 — CH 2 




5°°-5i° 


0I7506 (20 ) 


Methyl cyclobutane 


CH 2 — CH — CH 3 
\ 1 
CH 2 — CH 2 




390-42° 





Cyclohexane 


CH 2 — CH2 — CH 2 
CH 2 — CH 2 — CH 2 




8i° 


0.7783 (20°) 


Methyl cyclopentane 


CH 2 — CH 2 
1 >CH 
CH 2 — CH 2 


-CH 3 


7 2° 


0.7508 (20°) 


Cycloheptane 


CHo — CH 2 — CHo 
I " >CH 2 
C>H 2 — CH 2 — — CH 2 


118° 


0.809 (20 ) 


Methyl cyclohexane 


CH 2 — CH 2 — CH — 
CH 2 — CH 2 — CH 2 


-CH 3 


IOI° 


0.7694 (20 ) 


1.2 Di-methyl cyclohexane 


CH 2 — CH 2 — CH- 
CH 2 — CH 2 — CH — 
CH 2 — CH 2 — CH — 
CH S - CH — CH 2 


CH 3 
"CH 3 
-CH 3 


116 — 118 


o.7733 (20 ) 


1.3 Di-methyl cyclohexane 




120° 


0.769 (i9°) 



I 

CH 3 
CH 2 — CH 2 — CH — CH 3 
1 4 Di-methyl cyclohexane CH — CH 2 — CH 2 119 — 120 0.769(18°) 

CH 3 

A considerable number of other cyclic hydrocarbons of 
this series are known. 



CYCLOPROPANE. 83 

In the second series of hydrocarbons having the general 
formula C w H 2w instead of the double union between adjacent 
carbon atoms which is characteristic of the ethylene series, 
the carbon atoms are united to form a ring-like structure. 
Since these compounds and their derivatives, especially 
when the ring contains four or more carbon atoms, resemble 
compounds of the methane series rather than those of the 
ethylene series, they are given the same names as the 
former, but with the prefix cydo. The application of this 
nomenclature will be apparent from the table. 
CH 2 

Cyclopropane, | > CH 2 . This is prepared by warming 
CH 2 
1.3 dibrompropane (trimethylene bromide), CH 2 Br— CH 2 — 
CH 2 Br, with alcohol of 75 per cent and zinc dust. 
Cyclopropane is a gas which liquefies under a pressure of 
five or six atmospheres. It combines directly with bromine 
to form 1.3 dibrompropane, but the reaction takes place 
less easily than that of propene, CH 3 CH = CH 2 , with 
bromine. This reaction, as well as its method of forma- 
tion, demonstrates its structure. It combines with hydriodic 
acid to form i-iodo-propane. Propene, on the contrary, 
gives 2-iodo-propane, CH 3 CHICH 3 . 

Cyclopropane does not reduce a cold, neutral solution of 
potassium permanganate. Members of the ethene series 
and their derivatives reduce such a solution instantly. As 
the test is easily applied, it serves as a very useful, 
practical means of diagnosis for distinguishing the two 
classes of compounds. (Baeyer, Ann. Client. (Liebig), 245, 
146.) 

Cyclobutane has not been prepared, but the possibility of 
its preparation is rendered almost certain by the preparation 
of methylcyclobutane from 1 , 4-dibrompentane and sodium. 



8 4 


ORGANIC CHEMISTRY. 




CH 2 — CH CH. 




CH 2 BrCH 2 CH 2 CHBrCH 3 + 2 Na = | | 

CH 2 — ^H 2 




+ 2 NaBr. 



Methyl cyclobutane does not combine directly with hy- 
driodic acid, and all of the properties of the derivatives of 
cyclobutane indicate that a ring containing four carbon 
atoms is more stable than one containing three. 

CH 2 -CH 2 
Cyclopentane, j > CH 2 , has been prepared by the 

CH 2 -CH 2 

following series of reactions : Adipic acid, 

CH 2 -CH 2 -C0 2 H 

I 
CH 2 — CH 2 - CQ 2 H, 

when distilled with lime gives cyclopentanon, 







CH 2 

1 

CH 2 - 


-CH 2 

> c=o 

-CH 2 


is gives, 


on 


reduction, cyclopentanol, 






CH 2 - 
1 


-CH 2 H 

>c< 



CH 2 -CH 2 OH, 

and this, when treated with hydriodic acid, yields iodo- 

CH 2 -CH 2 H 

cyclopentane, | > C < ; 

CH 2 -CH 2 I 

this, by another reduction, gives cyclopentane. 



HEAT OF COMBUSTION. ' 85 

Cyclohexane and Cycloheptane have been prepared from 

pimelic acid, 

CH 2 -CH 2 -CH 2 -C0 2 H 

I 
CH 2 - CH 2 — C0 2 H, 

and suberic acid, CH 2 -CH 2 -CH 2 -C0 2 H 

I 
CH 2 -CH 2 -CH 2 -C0 2 H, 

by means of similar reactions. 

Attempts to prepare cyclooctane have been, thus far, unsuc- 
cessful. It seems, therefore, that the series reaches a natural 
limit with the ring containing seven carbon atoms, and that 
rings containing a larger number of atoms will be prepared 
only with great difficulty, if at all. 

This fact, and also that of the stability of the five, six, and 
seven carbon atom rings, appear to be of fundamental impor- 
tance. They have given a strong support to a theory with 
regard to the structure of carbon compounds which was 
originally based on relations which were found to exist be- 
tween the optical activity of carbon compounds and their 
structure (see p. 137). 

Heat of Combustion. — The addition of a CH 2 group 
causes an increase of 158 Cal. to the heat of combustion of 
most hydrocarbons, and this might lead us to expect that the 
heats of combustion of the hydrocarbons of this series would 
be simply multiples of that quantity. 

For cyclohexane (C 6 H 12 ), 933.2 Cal. (155.5 X 6), and methyl- 
cyclohexane (C 7 H 14 ), 1095. Cal. (156.4 X 7), the values 
approximate those which we should expect on the supposi- 
tion that the hydrocarbons consist of CH 2 groups united 
together. It is interesting to notice that the heat of com- 
bustion is, however, somewhat less, and so the heat of 



86 ORGANIC CHEMISTRY. 

formation is greater than the calculated values. What is true 
of the molecular volumes of cyclic compounds (p. 42) ? 
Is there any probable connection between the two sets of 

faCtS? CH 2 

For trimethylene, >CH 2 , on the other hand, the heat 

CH 2 
of combustion (499.4 = 3 X 166.5) * s considerably greater, 
and the heat of formation is less than those calculated, indi- 
cating a condition of instability in the compound. It is of 
interest to notice, too, that the heat of combustion of pro- 
pene, CH 3 CH = CH 2 (p. 80), is practically identical with 
that of trimethylene or cyclopropane. 

Occurrence of Cyclic Hydrocarbons. — Cyclopentane, cyclo- 
hexane and their derivatives have been found in consid- 
erable amounts in Russian petroleum from the region of the 
Caucasus. Cyclohexane and many of its derivatives have 
been prepared by the reduction of derivatives of benzene. 
When benzene itself is reduced by means of hydriodic acid 
at a high temperature (280 ) it is converted, in part at 

CH 2 CH 2 
least, into methylcyclopentane, | > CH CH 3 (Zelinsky, 

CH 2 CH 2 
Ber. d. Chem. Ges. 28, 1023 ; 30, ^>^). This fact is of espe- 
cial interest from its bearing on the theory of the structure of 
cyclic compounds according to which a saturated ring con- 
taining five carbon atoms should be more stable than one 
containing six atoms (p. 193). 

Laboratory Exercises. 

The saturated cyclic hydrocarbons are not very easily pre- 
pared. Cyclopropane and cyclohexane would be as well adapted 
as any for illustrative work. 



ACETYLENE. 



87 



CHAPTER VI. 



SERIES C M H 2w _ 2 , C n U 2n _„ and C H H 2fl . 

ACETYLENE SERIES, C„H 2w _ 2 . 











Boiling 


Specific 










Point. 


Gravity. 


Acetylene 


CH = CH 






-84° 


0.451 (o°) 


Allylene 


CH,— C = CH 












Propadiene 


CH 2 — C — CH 2 












3-Butine 


CH = C — CH 2 - 


CH 3 


14° 





2-Butine 


CH 3 — C = C — CH 




i 7 °-i8° 





1,3-Butadiene 


CH 2 =CH — CH 


= 


CH 2 









Valylene 



SERIES C„H 2re _. 

CH 3 - CH = CH — C = CH(?) 



SERIES C„H 2re _ 6 . 

Di-propargyl, 

(i,S-Hexadiine) CH = C — CH 2 — CH 2 — C = CH 86°— 87 
2,4-Hexadiine CH 8 — C = C — C = C — CH 3 129 — 130 (?) 



0.819 (o°) 



Acetylene, CH= CH, and acetylidene CH 2 =C (?) — Acetylene 
is formed in small amounts when carbon and hydrogen are 
brought together at the temperature of the electric arc 
(3000 - 3500 ). 

When calcium carbonate is heated with carbon, in an 
electric arc, calcium carbide, CaC 2 , is formed. This gives, 
on treatment with water, acetylene and calcium hydroxide. 

CaC0 3 + 4 C = CaC 2 + 3 CO 
CaC 2 + 2 H 2 = Ca(OH) 2 -f C 2 H 2 . 

This method of preparation is commercially important as 
a means of making acetylene for illuminating purposes. 



88 ORGANIC CHEMISTRY. 

Acetylene is also formed by the electrolysis of fumaric 
or malei'c acid. Both of these acids have the structure, 
CH-C0 2 H 
I! > (P* 2 57) an d are separated by electrolysis into 

CH - C °* H CH-CO, ' 

hydrogen and the complex ion, || . The latter then 

CH-C0 2 
decomposes into acetylene CH = CH and carbon dioxide, 
the decomposition being somewhat analogous to that of acetic 
acid (p. 61). This method of preparation, together with the 
synthesis of fumaric acid from acetylene iodide through the 
following series of compounds, 

CHI CH-CN CHC0 2 H 

II - II - II 

CHI CH-CN CHC0 2 H 

furnish satisfactory evidence that the hydrogen atoms in 
acetylene are combined with different carbon atoms. 

Acetylene is formed in small amounts when a Bunsen 
burner " snaps back " so that the gas burns in contact with 
a moderately cool surface and with a limited supply of air. 
If the products of combustion are passed through an am- 
moniacal solution of cuprous chloride a precipitate of copper 
carbide, Cu 2 C 2 (often called copper acetylide), is formed. 
From this, acetylene may be regenerated by treatment with 
dilute hydrochloric acid, or with a solution of potassium 
cyanide. 

Acetylene may be prepared by treating ethylene bromide 
with alcoholic potash or, better, with a solution of sodium 
ethylate in absolute alcohol. 

CH 2 Br-CH 2 Br + 2 NaOC 2 H 5 = 

CH = CH + 2 Na Br-f 2 C 2 H 5 OH. 



ACETYLENE. 89 

This method of preparation is similar to the preparation 
of butene from butyl iodide (p. 80). 

Acetylene is a gas which liquefies at i° under a pressure 
of forty-eight atmospheres. It is usually described as having 
a pungent, disagreeable odor, and the unpleasant odor 
emitted by a Bun sen burner when burning at the base has 
been ascribed to the acetylene which is one of the products 
of such combustion. It seems to have been established, 
however, that pure acetylene has a garlic-like but not a pen- 
etrating odor. Professor Nef has suggested that the gas 
obtained by some processes may be a mixture of true acety- 
lene, CH = CH, with acetylidene, CH 2 = C. He considers 
that the latter would have a penetrating, disagreeable odor 
and be extremely poisonous. Pure acetylidene has not been 
obtained, but a number of compounds supposed to be sub- 
stitution products of the body have been prepared. The 
evidence as to their structure is not, however, altogether sat- 
isfactory. 

Acetylene combines directly with chlorine or bromine to 
form 1,1,2,2, tetrachlor-, or tetrabrom-ethane, CHBr 2 CHBr 2 , 
respectively. If silver acetylide, Ag 2 C 2 , is treated with bro- 
mine, however, tetrabrom-ethylene, C 2 Br 4 , is formed. 

Structure of Acetylene. — The structural formula of acety- 
lene is usually written CH = CH. Apart of the evidence 
that the hydrogen atoms are united with different carbon 
atoms has been given. The significance of the triple union 
represented between the two carbon atoms is not clear. 
That it does not mean that the carbon atoms are held to- 
gether more firmly than they would be held by a single 
union is evident from the chemical properties of acetylene 
and its homologues. That three of the four powers of com- 
bination possessed by each carbon atom are used in holding 



90 ORGANIC CHEMISTRY. 

the two carbon atoms together seems probable, but such a 
form of union is evidently unstable. 

The instability of the molecule is especially evident from 
the heat of combustion of acetylene which is 310.1 Cal. 
This gives for acetylene a negative heat of formation of 
— 47.8 Cal. This means that 26 grams of acetylene would 
evolve 47.8 Cal. if decomposed into hydrogen gas and car- 
bon. This fact, which, a few years ago, possessed only a 
theoretical interest, has become of great practical impor- 
tance, since it indicates that acetylene may decompose ex- 
plosively under some conditions. The gas cannot be stored 
safely under a pressure exceeding two atmospheres, and 
especially it cannot be commercially used in a liquefied 
form. 

Other hydrocarbons having the general formula, C n H 2 „_ 2 , 
may be divided into four classes : 

1. True homologues of acetylene, or open-chain com- 
pounds containing one triple union, as allylene, 

CH 3 - C = CH. 

2. Open-chain compounds having two double unions, as 
propadien, CH 2 = C = CH 2 . 

3. Cyclic compounds having one double union, as cyclo- 



hexene, 



CH 2 -CH 2 -CH 



4. Dicyclic compounds. To this class, dekahydronaph- 
thalene, C 10 H 18 , probably belongs, but very few hydrocar- 
bons of the class are known. 

Nomenclature. — In the official nomenclature, hydrocarbons 
of the marsh-gas series and saturated cyclic compounds take 



TERPEN ES. 91 

names ending in -ane, the latter with the prefix cyclo. Com- 
pounds having double unions take names ending in -ene, or, 
if two or three double unions are present, the endings 
-diene, -triene, etc. Thus CH 2 = C = CH 2 is propadiene. Com- 
pounds having triple unions take names ending in -ine ; thus 
CH = C — CH 3 is, officially, propine. Unfortunately, the 
official names are not always used, and it is often necessary 
to learn two names for the same compound. 

Series C M H2 U _4 and C n R 2n _Q. — Hydrocarbons with open 
chains, and containing less hydrogen than the members of the 
acetylene series, present few facts that are new in principle 
or that require consideration here. In general the instabil- 
ity of the compounds increases with the decrease of hydro- 
gen. Some compounds containing several triple unions are 
so unstable as to be explosive. All of the compounds under 
consideration are spoken of as unsaturated, because they all 
add bromine, iodine or the halogen acids directly, without 
loss of hydrogen. They are converted, by such addition, 
into substitution products of the marsh-gas series. 

Hydrocarbons containing the group CH adjacent to a 
triple union give precipitates with an ammoniacal solution 
of a silver or of a cuprous salt. No other hydrocarbons do 
this. 

Terpenes. — A considerable number of hydrocarbons which 
have the formula C 10 H 16 are found in nature or are ob- 
tained from natural products. These bodies are unsaturated, 
as shown by their conduct toward permanganate, and by 
the fact that they combine directly with one or two mole- 
cules of hydrochloric acid. That they never combine with 
more than two molecules of the halogen acids proves that 
they are cyclic/ compounds. (Why?) It was formerly sup- 



92 ORGANIC CHEMISTRY. 

posed that the terpenes are in most cases derivatives of 
cyclohexadiene, 

CH 



/ 

CH 2 

i 


CH 

i 


CH 


1 
CH. 


\\ 


/ 
CH 



having two hydrogen atoms replaced by a methyl and a propyl 
group respectively and with the double unions in varying 
positions. The more recent work with the group indicates 
that some of the hydrocarbons contain a double ring and that 
in others the double unions may be in the side chain rather 
than in the nucleus. It is probable, also, that some of them 
contain a ring of five carbon atoms, instead of six. A number 
of chemists are at present engaged with the study of the group, 
which presents unusual difficulties. Very few syntheses have 
thus far been effected in the group ; and until some of the 
more important terpenes or their derivatives are prepared 
artificially, the knowledge of these compounds is likely to 
continue unsatisfactory. The study of the group has been 
rendered more complex and difficult by the ease with which 
many members of it undergo molecular rearrangements, 
sometimes with radical changes of structure. 

Laboratory Exercises. 

i. Preparation of acetylene by two or three different methods. 
Preparation of copper acetylide. 

2. Preparation of pinene hydrochloride Ci H, 7 Cl, or " artificial 
camphor " from turpentine. 



ALIPHATIC AND AROMATIC COMPOUNDS. 93 



CHAPTER VII. 
BENZENE SERIES, CLH 



2 m — 6" 



Aliphatic and Aromatic Compounds. — The compounds of 
this series, and other compounds which are closely related to 
them, present so many peculiarities that it has been customary 
to separate organic compounds, for discussion, into two great 
classes, the " aliphatic," # or open-chain compounds, and the 
"aromatic" compounds. Formerly very few reactions were 
known by which it was possible to pass from one class of 
compounds to the other in such a manner as to establish any 
relation in the structure of the compounds involved. A con- 
siderable number of such reactions are now known, and with 
their discovery some of the reasons for a separate treatment 
have disappeared. More than one-half of the carbon com- 
pounds at present known belong to the aromatic series. 

No hydrocarbon nor any derivative of a hydrocarbon hav- 
ing the distinctive properties of this group, and containing 
less than six carbon atoms, is known. Also it is possible, by 
means of simple and well understood reactions, to break down 
very many compounds of the series in such a manner as to 
obtain compounds containing only six carbon atoms in the 
molecule. The simplest hydrocarbon which can be obtained 
by reactions of this kind is benzene, C 6 H 6 . 

We must look upon benzene, therefore, as the simplest and 
typical compound of the series, and the determination of its 

* The word aliphatic is derived from the Greek aAet^ap, fat, and is based on the 
fact that the more important acids obtained from the natural fats are derivatives of the 
marsh-gas hydrocarbons. 



94 ORGANIC CHEMISTRY. 

structure has acquired a very unusual interest. It must be 
admitted, at the outset, that this problem has not yet received 
a complete and satisfactory solution, though there is probably 
no question of structure which has received more careful 
attention and certainly none to which a more thorough dis- 
cussion has been given. 

Structure of Benzene. — ■ The more important experimental 
facts upon which the discussion of the structure of benzene 
must be based are as follows : 

i. Benzene, and all substances which can be considered as 
belonging to its class, contain at least six carbon atoms. This 
has been already stated above. 

2. By the action of chlorine or bromine on benzene in 
direct sunlight, hexachlorbenzene, C 6 H 6 C1 6 , or hexabromben- 
zene, C 6 H 6 Br 6 , is formed. Reducing agents cause the addi- 
tion of six hydrogen atoms to some derivatives of benzene. 
Thus the hydrogen evolved from boiling amyl alcohol and 
sodium converts benzoic acid, C 6 H 5 C0 2 H, into hexahydroben- 
zoic acid, C 6 H n C0 2 H. Since chlorine, bromine or hydrogen 
would convert an open-chain compound into a derivative of 
hexane, C 6 H 14 , these facts can be satisfactorily explained only 
by supposing that benzene contains a ring of carbon atoms, 
thus : q 

/ \ 
C C 

I I 

c c 

c 

The truth of this conclusion has been further demonstrated 
by the preparation of hexahydroisophthalic acid, 

C0 9 H 



C 6 H 10 < 



C0 9 H' 



STRUCTURE OF BENZENE. 95 

both by reactions which show that it is a derivative of cyclo- 
hexane, and by the reduction of isophthalic acid, 

r H , C0 2 H 
64 < C0 2 H' 

which is a simple derivative of benzene. 

3. There is but one mono-substitution product of benzene 
with a given substituent ; i.e., there is but one mono-bromo- 
benzene, C 6 H 5 Br ; but one mononitrobenzene, C 6 H 5 N0 2 ; but 
one benzoic acid, C G H 5 C0 2 H. 

That four different hydrogen atoms in the benzene mole- 
cule may be replaced by the same group, and that the four 
compounds obtained are not different but identical, have 
been demonstrated as follows : 

Phenol on treatment with phosphorus pentabromide gives 
monobrombenzene. 

C 6 H 5 OH + PBr 5 = C G H 5 Br + POBr 3 + HBr. 

Monobrombenzene gives, with sodium and carbon dioxide, 
sodium benzoate. 

C 6 H 5 Br + C0 2 + 2Na = C 6 H 5 C0 2 Na + NaBr. 

Benzoic acid gives, with nitric acid, three different nitro- 
benzoic acids. 

C 6 H 5 C0 2 H + HN0 3 = C 6 H 4 ( £0 2 H + H 2 0. 

These nitrobenzoic acids can be readily separated by 
crystallization of their barium salts. Each gives by reduc- 
tion a different amino-benzoic acid. 

C « H < Nof + 6 H = C °< NHf + 2 H A 



96 ORGANIC CHEMISTRY. 

P2ach amino-benzoic acid gives with nitrous acid a different 
hydroxy-benzoic acid. 

C « H * \ NH 2 H + HN ° 2 = CeH4 \ OH H + H2 ° + Na> 

It is evident that in each hydroxy-benzoic acid the hy- 
droxyl groufj must replace a different hydrogen atom of the 
benzene molecule ; and, also, since the carboxyl occupies 
the place of the original hydroxyl of the phenol, that each 
of these hydrogen atoms is different from that replaced by 
the original hydroxyl. Now each hydroxy-benzoic acid, on 
distilling with soda-lime, gives a phenol identical in every 
respect with the original phenol. 

C 6 H 4 7 £^ H + 2 NaOH = C 6 H 5 OH + Na 2 C0 3 + H 2 0. 
The relations will, perhaps, be clearer from the following 



diagram : 



Melting 
Point. 

^<£of J 47° 
C 6 H 5 OH -> C 6 H 5 Br -> C 6 H 5 C0 2 H -> C 6 H 4 (£0 2 H 141 

\ r H /C0 2 H 

CeJ:l4 \N0 2 236 

Melting Melting 

Point. Point. 

„„/C0 2 H ., „/C0 2 H ,„ 

^ C ' H SNH, '« -* C « H SOH ^ 6 \ 

->C,H 4 (^ i74°-*C 6 H 4 (^ H 2 oo°_*C 6 H 6 OH 

-* /- u / CO.H „ . „ u / C0 2 H „ •* 

^ C « H <XN H ; i8 7 »->C g H 4x0 ^ no 



STRUCTURE OF BENZENE, 97 

The proof given under 4 below, that when one hydrogen 
atom in benzene has been replaced by some atom or group 
there are two pairs of hydrogen atoms symmetrically placed 
with regard to that group, completes the demonstration that 
the relation of any hydrogen atom in benzene to the rest of 
the molecule is like that of every other. 

There are only two arrangements which meet the require- 
ments that benzene must contain a ring of six carbon atoms, 
and that the hydrogen atoms must be symmetrically placed. 
These are : 

CH 2 CH 

/ \ / \ 

C C CH CH 

I I and I I 

CH 2 CH 2 CH CH 

\ / \ / 

C CH 

4. With a given pair of substituents there may be three, 
and only three, bisubstitution products of benzene ; thus 
there are three bibrombenzenes, C 6 H 4 Br 2 , three nitrobenzoic 

acids, C 6 H 4 N0 2 , etc. 

The first part of the statement is, of course, demonstrated 
by the existence of three isomeric bisubstitution products of 
benzene, three illustrations of such cases being given above. 

That there are only three bisubstitution products in a 
given case is demonstrated as follows : — 

One of the brombenzoic acids, C 6 H 4 ^ 2 , gives by 

treatment with nitric acid two different nitrobrombenzoic 

/C0 2 H 
acids, C 6 H 3 — Br , but these give by reduction the same 

\N0 2 

aminobenzoic acid, C B H 4 x '^ . Since the nitrobromben- 
' b 4 \NH 2 



98 ORGANIC CHEMISTRY. 

zoic acids are different, the nitro groups in them must oc- 
cupy different positions with regard to the bromine, but 
the two positions must bear the same relation to the car- 
boxyl. 

Further, there is a methylbrombenzene, C 6 H 4 -^ ? , which 

gives, by oxidation, the same brombenzoic acid mentioned 
above, and which must, therefore, have the bromine and 
methyl in the same relation as the bromine and carboxyl 
in the brombenzoic acid. The same methylbrombenzene 
can be prepared from a given methylaminobrombenzene 

/CH 3 
C 6 H 3 — Br , by replacing the amino group with hydrogen. 

\NH 2 
The acetyl derivative of this methylaminobrombenzene 

/CH 3 

/ Br 

gives with nitric acid a nitro derivative, C 6 H 2 ^-^ , 

\ NHC 2 H s O 

this, by elimination of the acetamino-group, a methyl nitro- 

/CH 3 , 

brombenzene, C 6 H 3 — Br , and this, by reduction, a methyl, 
\N0 2 

/ Cl-T 

aminobenzene, C 6 H 4 attt 3 * The last compound gives, by 

replacement of the amino group with bromine, the same 
methylbrombenzene as that mentioned above. Since the 
nitro group must replace a different hydrogen atom from 
that originally replaced by the bromine, there must be a 
pair of hydrogen atoms symmetrically placed with regard 
to the methyl. As the position of the bromine atom does 
not correspond to that of either one of the first pair of sym- 
metric hydrogen atoms, it follows that there are two pairs 
of such hydrogen atoms. 



STRUCTURE OF BENZENE. 99 

The relations will be clearer from a study of the following 
diagram.* 

r „ C0 2 H , r „ / R C °^ H ' 
QH 4 < ->C 6 H 3 -Br 2 

• X N0 2 3 \ rw C0 2 H 

\ /CO.H 1 /» ^ M4< NH 2 ( 3 or 4 ) 

C«H, —Br 2 



\ 



N0 2 4 



CH, 1 _ CH, 1 „„ / CHs ' 



C 6 H 4 < ^ ^ _*n C eH 4 < XTri - . <- C 6 H 3 -Br 2 

t X N0 2 5 

CH 3 1 

Br 2 



Br (2 or 5) * *-NH 2 5 

CH 3 

C 6 H 3 -Br 2 > C 6 H 2 < 

N NHC 9 HX> \ 



N0 2 5 

NHC 2 H 3 



The conditions outlined last, that benzene contains two 
pairs of hydrogen atoms symmetrically related to an initial 
hydrogen atom, and a third which bears a different relation 
from that of either of the four, together with the conditions 
previously named, can only be met by supposing that 
benzene contains a ring of six CH groups, thus : 

tt 
CH 

/ \ 

(6) CH CH (2) 

i I 

(5) CH CH (3) 

\ / 

CH 

(4) 

* The numbers are used here in purely consecutive order, so that it may be easier 
to follow the positions. The brombenzoic acid is the meta compound, and the nitro 
group enters in the ortho position with regard to the carboxyl. 

iLsfC. 



IOO ORGANIC CHEMISTRY. 

In this formula it will be seen that positions 2 and 6, and 
also 3 and 5. are symmetrically placed with regard to 1, 
while the position 4 is different from any other. 

Such positions as 1.2 or 2.3 or 1.6 are called ortho ; 1.3 
or 2.4 or 2.6 are called meta; and 1.4 or 2.5 or 3.6 are 
called para. The practical means used to distinguish the 
different positions will be discussed below. 

5. The order of the carbon atoms in benzene is the same 
as in cyclohexane ; that is, ortho carbon atoms are adjacent, 
meta carbon atoms are separated by one carbon atom, and 
para carbon atoms are separated by two carbon atoms. 

CO H 

Isophthalic acid, C 6 H 4 < / ^ / ^. 2 , which is a meta com- 

2 CO H 

pound, gives hexahydroisophthalic acid, C 6 H 10 < 2 , by 

C0 2 H 

reduction. When the ethyl ester of pentanetetracarboxylic 

. . ,Y,-r CH 9 CH(COoC 2 Hr)r, . . .. 

acid, CH 2 < CH CH / CO c R ( > 1S treated with sodium 

ethylate and methylene iodide CH 2 I 2 1.1, ^.^ cyclohexane 
tetracarboxylic ester, 

CH 2 
/ \ 
CH 2 C = (C0 2 C 2 H 5 ) 2 

I I 

CH 2 CH 2 

\ / 

C = (C0 2 C 2 H 5 ) 2 

is formed, and this gives by saponification and heating (see 
p. 251) the same hexahydroisophthalic acid, 

CH 2 
/ \ 

CH 2 CH-C0 2 H 

I I 

CH 2 CH 2 

CH-C0 9 H 



'STRUCTURE OF BENZENE. 



IOI 



which is formed by the reduction of isophthalic acid. A 
similar proof for the ortho position is given by the formation 
of pimelic acid by the reduction of salicylic acid, thus : 



CH-CH = C-C0 9 H 



CH 2 — CH 5 



-CH 2 -C0 2 H 



CH-CH = C-OH 

Salicylic acid. 



CH 9 — CH 9 



Pimelic acid. 



-C0 2 H 



For the para position a similar proof of the order of the 
carbon atoms is given by the formation of the ethyl ester of 
dihydroxyterephthalic acid when succinylo-succinic ester is 
treated with bromine : 

OH 



CH 2 -CO-CH-C0 2 C 2 H 5 

I I 

CH-CO-CH, 



C0 2 C 2 H 5 

Succinylo-succinic ester. 



CH-C *= C-C0 2 C 2 H 5 



C— C = CH 

OH 
C0 2 C 2 H 5 

Dihydroxyterephthalic ester. 



Ladenburg's Prism Formula. — The conclusion of this 
paragraph is of especial interest from its bearing on Laden- 
burg's prism formula, which was looked upon with favor by 
many chemists a few years ago. 

This is, 

(4) 
C±l l^tl 

/ 

(5)CH 




Since the position 4 is the only one which is different 
from all others in its relation to position 1, it must be para 



102 ORGANIC CHEMISTRY. 

to that position. In the same way positions 2, 5, and 3, 6, 
must be para. Further, since the positions 1, 3, admit 
of three other positions (4 or 6, 2 and 5) with regard to 
them, these positions must be meta (see below). 1, 2 and 1, 
6, must for a similar reason be ortho. But it is impossible 
that a compound of this structure should give, by reduction, 
a ring containing six carbon atoms in which the atoms 1 
and 2 are adjacent. The formula is therefore impossible, 
although it explains satisfactorily most of the compounds 
which contain the benzene nucleus. 

6. The low molecular volume of benzene has been taken 
as evidence that benzene must contain nine single unions 
between the carbon atoms. (Schiff, Ann. Ckem. (Liebig), 
220, 303.) The effect of the cyclic structure in causing a 
decrease of the molecular volume appears, however, to have 
been overlooked in the discussion (see p. 42). 

The molecular refraction corresponds to that which we 
should expect for a compound with three double unions. 
(Briihl, Zeit. phys. Chem. 1, 348.) 

The heat of combustion is given as 776 Cal. by Berthe- 
lot, as 779.5 Cal. by Stohmann. The heat of combustion of 
72 grams of carbon is 8.08 X 72 = 581.8 Cal.; that of 6 
grams of hydrogen is 34.2 X 6 = 205.2, or together 72 grams 
of carbon and 6 grams of hydrogen would give 787. Cal. 
This gives a heat of formation for benzene of — 7.5 or — 11. 
Cal. The heat of formation of cyclohexane, C 6 H 12 , is + 59 
Cal. (see p. 85). It seems, therefore, when we consider the 
heats of formation of ethane and ethylene (p. 81), as well as 
those of cyclohexane and of benzene, that the results are 
more consistent with the supposition of three double unions 
than with that of nine single unions. Thomsen, Ther- 
mochem Untersuch. 4, 6, and DiefTenbach, Zeit. phys. Chem. 
5, 574, however, draw an opposite conclusion. 



FORMULA OF BENZENE. 1 03 

Formula of Benzene. — When an attempt is made to assign 
a formula to benzene which shall agree with all of the facts 
given above, and also give expression to the quadrivalence 
of carbon, very grave difficulties are encountered. The two 
formulae which at present receive serious consideration are 
those of Kekule and 'of Claus. The latter is known in some 
of its interpretations as the " diagonal " and as the " centric " 
formula. 



CH 
/ ^ H 

HC CH 

II I 

HC CH 



II 
C 



c 




x: H 



c h 



\ // H C 

CH - C 

H 

Kekule. Claus. 

Many variations of these formulae have been given ; but 
they all come back, for their essential basis, to one or the 
other form. See Kekule, Ann. C/iem. (Liebig), 162, 86 ; 
Baeyer, Ber. chem. Ges. 23, 1272 ; Sachse, Ber. chem. Ges. 
21, 2530; Zeit. phys. Chem. 11, 214; Armstrong, Proc. Chem. 
Soc. (London) iSpo, 101 ; Marsh, Phil. Magazine, 26, 426 
(1888); Collie,/. Chem. Soc. (London), 71, 1013 (1897); 
Erlenmeyer, Jr. Ann. Chem. (Liebig), 316, 57; C. Graebe, 
Ber. chem. Ges. 35, 526 (1902). 

The most serious objection to Kekule's formula is that it 
represents positions 1, 2 and 1, 6 as different, the carbon 
atoms being connected by a double union in the one case 
and by a single union in the other. To meet this difficulty 
Kekule supposed {Ann. Chem. (Liebig), 162, 86), that the 
union between the carbon atoms is dynamic rather than 
static, and that the double and single unions may be 



104 ORGANIC CHEMISTRY. 

considered as continually shifting their places. (See also 
Knorr, Ann. Chem. (Liebig), 279, 196.) A second objection 
to the formula is that it represents benzene as an unsaturated 
compound, while in all of its most common and important 
characteristics it conducts itself as a saturated body. Also, as 
soon as two hydrogen atoms have been added to benzene or 
to any of its derivatives they conduct themselves in all respects 
as other unsaturated compounds do. Benzene and its deri- 
vatives with saturated side-chains are without effect on a 
cold dilute solution of potassium permanganate while dihy- 
drobenzene, tetrahydrobenzene and their derivatives reduce 
such a solution instantly. 

The objection to the diagonal or centric formula is that 
if the carbon atoms are considered as in the same plane the 
diagonal unions must, for geometric reasons, be different 
from the other unions. Even if a stereomeric form # be 
found which meets this objection, the chemical evidence 
given demonstrates that when hydrogen is added to benzene 
or its derivatives it is the centric unions which are dis- 
solved, while what may be called the cyclic unions always 
remain. 

The choice among these formulae and their interpreta- 
tions must be considered at present as uncertain. The 
proper attitude for a beginner, at least, is to look upon the 
question as still an open one, and gradually to gather in his 
mind evidence as to one view or another till enough has 
been accumulated for an independent judgment. 

So far as the practical investigation of aromatic com- 
pounds is concerned, the questions last discussed have little 
interest. In the study of these compounds the cyclic unions 
are the only ones which require consideration, for almost all 
cases. 

* That is, an arrangement of the atoms in space. 



ORTHO, MET A, AND PARA POSITIONS. 



05 



Ortho, Meta, and Para Positions. — In the study of these 
compounds, a question of great practical importance is as to 
how the three positions, ortho, meta, and para may be distin- 
guished. An answer to this question, based upon the relation 
to derivatives of cyclohexane, has already been given. It is 
possible, however, to secure an entirely independent answer 
from the study of " aromatic " compounds alone. 

If we suppose two hydrogen atoms in benzene to be re- 
placed by the same atom or group, examination of the result- 
ing formulae will show that with an ortho compound a third 
substituent may give two isomeric compounds, with a meta 
compound three such compounds may be obtained, while a 
para compound gives only one. Thus : 



gives 




and 



gives 



and 

x y 



gives 



106 ORGANIC CHEMISTRY. 

The following is an illustration of how these principles are 
applied. "There are six diaminobenzoic acids, 



NH 



Two of these give a diaminobenzene, C 6 H 4 (NH 2 ) 2 melting at 
io2°. This must be the ortho compound. Three give a 
diaminobenzene melting at 63 , evidently meta; and one 
gives para-diaminobenzene melting at 140 . 

Having once determined to which class, ortho, meta, or 
para, a few derivatives of benzene belong, the structure of 
other compounds can be determined by conversion into one 
of the known forms, or by conversion of a known form into 
the compound whose structure is to be determined. Thus 
the conversion of nitro compounds into amino compounds, 
of amino compounds into halogen derivatives, hydroxyl com- 
pounds and acids, and of halogen derivatives into hydro- 
carbons and acids, may be readily effected by reactions which 
will be given later. In such reactions it is assumed, of 
course, that the new group takes the position of the old one. 
In some cases, and especially in fusions with caustic potash, 
this is not always true ; and at one time some confusion 
arose from this cause, so that in the period 1867 to 1880 it 
is necessary to notice, in using the literature, that ortho and 
meta compounds are often interchanged. 

Trisubstitution products of benzene having adjacent 
groups are called " neighboring," or " vicinal;" those hav- 
ing two groups adjacent and a third separated from them 
are " asymmetric ; " while those with three separated groups 
are called " symmetric." 



BENZENE. 



107 



Neighboring 
(Vicinal) (v) 



Asymmetric (a) 



Symmetric (s) 



Benzene Series. 



Benzene 
Toluene 

o-Xylene 

m-Xylene 

p-Xylene 

Ethyl benzene 

Hemellithene 
v-Trimethyl benzene 

Pseudocumene 

asym. Trimethyl benzene 

Mesitylene 

sym. Trimethyl benzene 

Cumene 

Isopropyl benzene 

Durene 

1.2.4.5. Tetra methyl benzene 

Cymene 
p-Isopropyl benzene 



C H 4 



C,;H. 



Q>H 

/CH 3 (1) 
\CH 3 ( 3 ) 

/CH 3 (i) 

' r,l ' 4 \CH 3 (4) 

C 6 H 5 C 2 H fi 

/CH 3 (i) 

C 6 H S -CH 3 (2) 
NCH»(3) 

/CH 3 (.) 

C 6 H 3 — CH, (2) 

' \CH a (4) 

/CH,(i) 

C„H 3 -CH S (3) 

\CH, (s) 



C„H=CH; 



'CH 3 



Boiling Melting Specific 



\CH, 
C H2(CH 3 )4 
/CH 3 

\CH 3 



Point. 
80.36° 
in.° 

141-9° 

139-2° 

138. 
136.5° 

175° 
169.8 

164.5 
153° 



Point. Gravity, 



S-42 u 

—28° 
-54° 
i5° 



[90 — 194° 8o° 



0.8736- 
0.8656 

0.8766 

0.8655 

0.8635 
0.8683 

0.8787 
0.8694 



9.S C 



0.8564 " 



Only the most important hydrocarbons are given in this 
table. Many others are known. 

Benzene.* — C 6 H 6 . This hydrocarbon was first discovered 
by Faraday in 1825, in the liquid formed by compression of 

* Benzene and " benzine " are totally different substances. See p. 73. 



108 ORGANIC CHEMISTRY. 

oil-gas. It was first isolated from coal-tar by A. W. Hof- 
mann in 1845. It is formed by passing acetylene, C 2 H 2 , 
through a hot tube. It may also be prepared by heating 
benzoic acid, C 6 H 5 C0 2 H, with soda-lime : 

C 6 H 5 C0 2 Na + NaOH = Na 2 C0 3 + C 6 H 6 . 

Many of the earlier researches with benzene were carried 
out with material obtained in this manner. At present 
benzene is obtained almost exclusively from coal-tar. It 
is separated partly by fractional distillation, partly by shak- 
ing it with a small amount of concentrated sulphuric acid 
to remove thiophene, C 4 H 4 S, and finally by freezing it and 
pouring off the liquid portion. It boils at 80.4 , melts at 
5. 4 and has a specific gravity of 0.8736 2 ¥ °°. It is now 
prepared from coal-tar in very large quantities for use in 
manufacturing dye-stuffs and other commercial products. 
It is also present in illuminating gas, and is a very im- 
portant constituent in giving illuminating power to the gas. 
Recently, benzene and some of its homologues have been 
found in considerable quantities in California petroleum. 

Benzene and its homologues and related compounds are, 
undoubtedly, not present in the coal, but are formed during 
its distillation, very much as benzene is formed from acetyl- 
ene. The same compounds are formed when almost any 
kind of organic matter is subjected to destructive distillation 
at a high temperature. 

Toluene, C 6 H 5 CH 3 , is also present in considerable quan- 
tities in coal-tar, and is easily prepared from that source. 
It is also formed by the action of sodium on a mixture of 
monobrombenzene and methyl iodide. 

C 6 H B Br + CH3I + 2 Na = C 6 H 5 CH 3 + NaBr + Nal. 



TOLUENE. 109 

This is known as Fittig's synthesis ; by its means the real 
nature of the hydrocarbon was first demonstrated. 

Toluene, and its derivatives in which only the hydrogen 
of the side-chain (i.e. methyl) has been replaced, may be 
oxidized to benzoic acid, C 6 H 5 C0 2 H. The formation of 
acids by the oxidation of side-chains is one of the special 
characteristics of the series. A similar oxidation of side- 
chains has been very rarely observed in the case of aliphatic 
compounds. 

PIT 

Xylenes, C 6 H 4 < 3 . All three of the xylenes are con- 
CH 3 

tained in the coal-tar and may be prepared from it. If the 
fraction containing the xylenes is boiled for some time with 
dilute nitric acid (Sp. gr. 1.15), the ortho- and paraxylenes 
are mostly oxidized to acids which may be removed by 
washing with a solution of sodium hydroxide. A residue is 
left which consists mainly of metaxylene. On the other 
hand, by shaking with concentrated sulphuric acid, ortho- 
and paraxylene are left undissolved, while metaxylene is 

converted into a sulphonic acid, C 6 H 3 :, J^ 2 . For further 

\ S0 3 H 

details of the separations, the student is referred to larger 

works. 

By oxidation the xylenes give ortho-, meta-, and paratoluic 

y PIT 

acids, C 6 H 4 rr ?xri an d by further oxidation, (ortho) phthalic 

acid, (meta) isophthalic acid and (para) terephthalic acid, 

/ C0 2 H 
^ 6 4 \C0 2 H' 

Ethyl benzene, C 6 H 5 C 2 H 5 , gives by oxidation benzoic acid, 
C 6 H 5 C0 2 H ; and this is typical of aromatic hydrocarbons 
with side-chains containing more than one carbon atom. 



IIO ORGANIC CHEMISTRY. 

This principle may be used for the determination of struc- 
ture. What must be the structure of a hydrocarbon, C 9 H 12 , 
which gives isophthalic acid by oxidation ? What structures 
are possible for a hydrocarbon, C 10 H 14 , which gives parato- 
luic acid by oxidation ? 

/CH 3 (i) 
Pseudocumene, C 6 H 3 — CH 8 (2), is found in coal-tar, and 
\CH 3 ( 4 ) 
has been prepared both from monobrommetaxylene and 

monobromparaxylene by treatment with methyl iodide and 
sodium. How does this demonstrate its structure ? 

/CH 3 (i) 
Mesitylene, C 6 H 3 — CH 3 (3), is found in coal-tar, but is 

\CH 3 ( 5 ) 
most easily prepared by mixing acetone with concentrated 
sulphuric acid, and distilling the mixture. (See p. 191.) 

3 CH 3 COCH 3 - 3 H 2 = C 9 H 12 . 

Since the reaction is most easily explained by supposing 
that the positions of the methyl groups are symmetrical in 

/PIT \ 

mesitylene, the fact that mesitylenic acid, C 6 H 3 < 3 JL 

gives metaxylene by distillation with soda-lime was, at one 
time, used to prove that the methyl groups in that hydro- 
carbon are in the meta position. More satisfactory demon- 
strations are now known for the positions of the groups. 

/ CH 3 (1) 

Cymene, C 6 H 4 qh , is most easily prepared 

ch< ch;^ 

by warming camphor, C 10 H 16 O, with phosphorus pentoxide. 
It is formed, also, by the action of sodium, parabromiso- 

CH < 3 (1) 
propyl benzene, C 6 H 4 / CH 3 ^ ' , and methyl iodide. 

X Br (4) 



CYMENE. Ill 

Cymene is also formed by the action of chlorine on pinene 
(from turpentine). 

C 10 H 16 + 2 C1 = C 10 H 14 + 2HC1. 

Turpentine. Cymene. 

The preparation 1 of cymene from camphor and from tur- 
pentine has given it an unusual interest ; but the relation, in 
structure, to these compounds is not as close as was formerly 
supposed. 

Cymene gives by oxidation, according to the agents used 
or the conditions, paratoluic, terephthalic, cuminic, 

COoH 

CH 3 , 

CH 3 

hydroxyisopropyl benzoic, 



QH 4 / 

X CH< 



/C0 2 H 
C6H4 -C(OH)<g' 

acids, or paratolyl-methyl ketone, 
r tt / CHs 

^l^coch; 

Preparation of Hydrocarbons. — The hydrocarbons of this 
series are prepared : 

i. From coal-tar. 

2. By treating a mixture of a halogen derivative of an 
aromatic hydrocarbon with an alkyl* iodide and sodium. 
(Fittig's synthesis.) 

C 6 H 5 Br -f CH 3 I + 2Na = C 6 H 5 CH 3 + NaBr + Nal. 

Brombenzene. Methyl Toluene, 

iodide. 

* The name "alkyl"" is used for univalent hydrocarbon radicals, especially for those 
of the aliphatic series, as methyl, CH 3 , ethyl, C 2 H 5 , etc. Vorlander,/. fir. Chem. 59, 
247, proposes to call the latter alfihyls, and similar radicals of the aromatics series, as 
C 6 H S , aryls. 



112 ORGANIC CHEMISTRY. 

This reaction is especially useful in the determination of 
constitution. 

3. By treating an aromatic hydrocarbon with an alkyl 
chloride or bromide and aluminium chloride. (Friedel and 
Craft's reaction.) 

C 6 H 6 + CH 3 CI + AICI3 = C 6 H 5 CH 3 + HC1 + A1C1 8 . 

A compound of the hydrocarbon with aluminium chloride, 
C 6 H 5 A1C1 2 , appears to be formed at first, and this reacts 
with the alkyl chloride. Accompanying the synthesis the 
reverse reaction may occur, as xylene may be converted into 
toluene, or toluene into benzene. 

4. By distilling acids or sulphonic acids with soda-lime, or 
by heating sulphonic acids with dilute sulphuric or concen- 
trated hydrochloric acid. 

C 6 H 5 C0 2 Na + NaOH = C 6 H C + Na 2 C0 3 . 

Sodium benzoate. Benzene. 

C 6 H 5 S0 3 H + HC1 + H 2 = C 6 H C + H 2 S0 4 + HC1. 

Benzene sulphonic acid* 

5. By the elimination of an amino group after formation 
of a diazo* compound or hydrazine. (See pp. 459 and 477.) 

(C 6 H 5 NH 2 ) 2 H 2 S0 4 + 2HN0 2 = (C 6 H 5 N 2 ) 2 S0 4 + 4 H 2 0. 

Aniline sulphate. Benzene diazonium sulphate. 

(C 6 H 5 N 2 ),S0 4 + 2 C 2 H 5 OH = 

2C 6 H 6 -f 2N 2 + H 2 S0 4 -f 2C 2 H 4 0. 

Aldehyde. 

6. By distilling a phenol with zinc dust. 

C 6 H 5 OH + Zn = C 6 H 6 + ZnO. 

Phenol. 

General Characteristics. — While halogen derivatives, sul- 
phonic acids and nitro compounds are formed from aliphatic 



GENERAL CHARACTERISTICS. 113 

hydrocarbons only with considerable difficulty, similar deri- 
vatives of " aromatic " hydrocarbons are easily prepared : 

C 6 H 6 + Br 2 = C 6 H 5 Br + HBr. 

Brombenzene. 

C 6 H 6 + H 2 S0 4 = C 6 H 5 S0 3 H + H 2 0. 

Benzene sulphonic 
acid. 

C 6 H 6 + HNO3 = C p H 5 N0 2 + H 2 0. 

Nitrobenzene. 

The resulting compounds, too, are much more stable in 
the aromatic series. While ethyl bromide, C 2 H 5 Br, and simi- 
lar compounds will react easily with ammonia and slowly 
with silver nitrate and water, the bromine of brombenzene, 
C 6 H 5 Br, is not at all affected by these reagents. The ease 
with which homologues of benzene are oxidized, and the 
resulting products, have already been considered. 

Laboratory Exercises. 

1. Preparation of benzene, toluene, and xylene by the fractiona- 
tion of the light oil of coal-tar. 

2. Preparation of benzene from benzoic acid. 

3. Preparation of toluene from monobrombenzene or of ^-xylene 
from bibrombenzene. 

4. Preparation of cymene from camphor. 

5. Preparation of paratoluic and terephthalic acids from cymene. 

6. Preparation of mesitylene from acetone. 

7. Preparation of phenol from salicylic and from ^-hydroxy- 
benzoic acids. 



H4 



ORGANIC CHEMISTRY. 



CHAPTER VIII. 
HYDROCARBONS RELATED TO BENZENE. 







Boiling 
Point. 


Melting 
Point. 


Specific 
Gravity. 


Styrene 


CeHgCH — CH 2 


144° 





20° 
0.9074— 
4 


Phenyl acetylene 


C 6 H 5 C=CH 


141.6 





20^ 
0.9295 — 
4 


Diphenyl 


C 6 H 5 - C fi H 5 


254° 


70.5 


73° 
0.9919— 
4 


Diphenyl methane 


§gj>CH 2 


26l° 


27° 


.26° 

1.0008 — 
4 


i, i Diphenyl ethane 


§§>CH-CH 3 


286° 







i, 2 Diphenyl ethane 


C fi H 5 — CH 2 
C 6 H 5 — CH 2 


284° 


52° 


1.0423(52°) 


Triphenyl methane 


(C 6 H 5 ) 3 CH 


359° 


9 2° 





Triphenyl methyl 


(C 6 H 5 ) 3 C 











Hydrindene 


I )CH 2 

\^ \ch/ 


176° 





0.957(15°) 


Indene 


\^ \ch/ 


180° 





1.040(15°) 


Naphthalene 


CO 

CH 2 — CH 2 


2l8. 12° 


80.06° 


i.i5i7d5 ) 


Acenaphtene 


i 1 


277-5° 


103° 


1.0300(103° 



CH„ 



Fluorene 



Anthracene 



^1 



COO - 



TR1PHENYL METHYL 




Phenanthrene ^^ T^"^| 34o° 99° 




Chrysene ^^ T^^T^l 44 8 ° 



Very many hydrocarbons are known which contain one or 
more benzene nuclei combined with groups derived from 
other hydrocarbons or with each other in a great variety of 
ways. Some of the typical combinations are given in the 
table. Only a few of these need receive further discussion 
here. 

Triphenylmethane (C 6 H 5 ) 3 CH is prepared by Friedel and 
Craft's reaction from benzene and chloroform. 

3 C 6 H 6 + CHCI3 + AICI3 = (C 6 H 5 ) 3 CH + 3 HC1 4- A1C1 8 

The hydrocarbon is of especial interest because of its 
relation to rosaniline and to phenol phthalein (p. 263). 

Triphenyl Methyl (C 6 H 5 ) 3 C is, at present, unique in that 
it is the only hydrocarbon known which contains an odd 
number of carbon atoms. It is formed when triphenyl- 
chlormethane (C 6 H 5 ) 3 CC1 is allowed to act upon zinc, sodium 
or mercury, with careful exclusion of air. When exposed 
to air or oxygen, the hydrocarbon is at once converted into 
ditriphenylmethyl peroxide (C 6 H 5 ) 8 C — O — O - C(C 6 H 6 ) 8 . 
It also combines directly with iodine forming triphenyl- 
iodomethane (C e H 5 ) 8 CI. (Gomberg, /. Am. Chem. Soc. 22, 
757 ; 23. 496; 24, 597.) 



n6 



ORGANIC CHEMISTRY. 



Naphthalene, 



CH CH 

// \ / ^ 

CH C CH 

i 1 I 



CH 



C 



^ 



CH 



CH 

\ // 
CH 



is found in considerable quantity in coal-tar. Its structure 
is demonstrated as follows : 

Naphthalene gives, on treatment with nitric acid, nitro- 
naphthalene ; and this, on oxidation, yields a nitrophthalic 

/C0 2 H (i) 
acid, C 6 H 3 — C0 o H (2). If nitronaphthalene is reduced, it 

. \N0 2 (3) 
gives amino-naphthalene, and this, on oxidation, gives phthalic 

CHNO .CH 7/ « 

^10 n 7 iNW 2 ^ 6 3 \ NO 

C 10 H 7 NH 2 -> C 6 H 4 (C0 2 H) 2 



CiqH 8 



Since amino derivatives of benzene do not lose the amino 
group on oxidation without its replacement by some other 
atom or group, these results can only be explained by sup- 
posing that naphthalene contains two complete benzene 
nuclei. This is only possible if two of the carbon atoms are 
common to the two nuclei. 

Naphthalene gives two mono substitution products, a and 
/?. The numbering of the carbon atoms is as follows : 




ANTHRACENE. 1 1 J 

The positions are named as follows : 



1.-2 = ortho. 


1.5 = ana. 


1.8 = peri. 


1.3 = meta. 


1.6= epi. 


2.6 = amphi 


1.4 = para. 


i.7 = kata. 


2.7 =pros. 



These terms are seldom used and are given only for 
reference. 

Naphthalene gives by reduction tetrahydronaphthalene. 



h H 2 

h ^\ ^-\ H, 



H H 2 



The derivatives of this hydrocarbon have an especial inter- 
est, because those having a substituent in the benzene 
nucleus show the aromatic characteristics, while those with 
substituents in the reduced nucleus are similar in their 
properties to the derivatives of cyclohexane. To the latter 
class of compounds the name " alicyclic " has been given. 
(Bamberger.) 



Anthracene, 








CH CH CH 


CH 


CH CH 


/ W / 
CH C 


\ // \ // 
C CH CH 




\ / \\ / \\ 
C C CH 


II 1 
CH C 


1 II or | 
C CH CH 




II 1 1 
C C CH 


\ // \ 
CH C 


/ w / w 

H CH 


CH 


/ \ n \ 

CH CH 



This hydrocarbon is found in small amounts in coal-tar, 
and is separated for use in the manufacture of alizarin, or 
" Turkey red." When a solution of bromphthalic anhydride 



n8 



ORGANIC CHEMISTRY. 



in benzene is treated with aluminium chloride, brombenzoyl 
benzoic acid is formed. 



Br 



CO 

/ \ 



O 4- 



\ / 

CO 



Br 



MCI3 



CO 



C0 9 H 



The brombenzoyl benzoic acid gives, with concentrated sul- 
phuric acid at 180 , bromanthraquinone, 




The bromanthraquinone yields, on fusion with caustic 
potash, hydroxyanthraquinone, 

OH 



and this, by oxidation, gives phthalic acid. Since the ben- 
zene nucleus of the phthalic acid is the one represented at 
the right in the formulae it follows that the carbonyl (CO) 
groups of anthraquinone are ortho in that nucleus as well as 
in the other. Since further, anthraquinone has been reduced 



PHENANTHRENE. 



119 



to anthracene by distillation with zinc dust, the structure of 
the latter is established. 

The most characteristic reaction of anthracene is the 

/CO 

formation of anthracminone, C 6 H 4 >C 6 H 4 , from it by 

direct oxidation. For the nomenclature of anthracene deri- 
vatives see p. 214. 



Phenanthrene, 


CH 






H 

C 


// 
CH 

i 
CH 




C 

1! 
C 


/ 


CH 

1 
C 


^ 


CH 


/ 


\ 


// \ 
C CH 

1 II 
CH CH 

^ / 
CH 



is also found in coal-tar. It is formed when a mixture of 
diphenyl, C 6 H 5 C 6 H 5 , and ethylene are passed through a 
heated tube. It gives, on oxidation, but less easily than 
anthracene, phenanthraquinone, 




120 ORGANIC CHEMISTRY. 

and this, on further oxidation, diphenyl-dicarboxylic acid, 
C 6 H 4 -C0 2 H 
| , in which both carboxyl groups are ortho to the 

C 6 H 4 C0 2 H 

point of union between the two phenyl groups. This gives 
proof of the structure. 

Laboratory Exercises. 

i. Preparation of triphenyl methane. 

2. Oxidation of naphthalene to phthalonic acid, 

/COC0 2 H 

6 4 \C0 2 H _ ' 

by means of potassium permanganate in alkaline solution and 
further oxidation of the latter to phthalic acid by manganese 
dioxide in acid solution. 

3. Preparation of anthracene from anthraquinone by distilling 
with zinc dust. 

4. Determination of the per cent of anthracene in a sample of 
coal-tar. 



DERIVATIVES OF THE HYDROCARBONS. 121 



CHAPTER IX. 

CLASSIFICATION OF DERIVATIVES OF THE 
HYDROCARBONS. 

Most carbon compounds containing other elements than 
hydrogen may be conveniently considered as derivatives of 
hydrocarbons. The following list of the more important 
fundamental forms of such derivatives is given for con- 
venience of reference : — 

Alcohols and phenols R — O — H 

Ethers R — O — R 

Aldehydes R-cf 

Ketones R — C — R 

II 
O 

Acids R — C. 

X 0-H 

^O 
Acid chlorides R — C ( 

^OOc^ 
Acid anhydrides R — C' X — R 

\ o / 

^O 
Esters R — C ; / 

\ O — R 

x>0 
Amides R — C' 

X NH 2 

^O 
Alkyl amides R — C x 

Imides R < £§ > NH 

/NHR 
Urethanes „ C = 

\0-C 2 H 5 

Cyanides or nitriles R — C = N 

Isocyanides or isonitriles ..• R — N = C 



122 



ORGANIC CHEMISTRY. 



Cyanates R — O — C = N 

Isocyanates R-N = C = 

Thiocyanates R — S — C = N 

Isothiocyanates or mustard oils R-N = C = S 

/ C1 
Amide chlorides R — C— CI 

X NH 2 

/CI 
Imide chlorides . .' R — C ' 

/O — R 
Imidoesters R — C . 

\\NH 

Amidines R — C v 

X NH 2 

^NOH 

Amidoximes R — C x 

X NH 2 

//° 

Hydroxy acids R — C — O — H 

\0 — H 

//° 

Ketonic acids R — C — C — OH 

II 
O 

or R — C — R — C0 2 H 

II 
O 

Halogen compounds RC1, RBr, etc. 

Nitro compounds R — N0 2 

Amines RNH 2 , R 2 NH, etc. 

Diazo compounds R — N = N 

CI 
or R — N = N — CI 
Hydrazo compounds R — NH — NH — R 

Azo compounds R — N = N — R 

Diazoamino compounds R — N = N — NHR 

Aminoazo compounds R — N=N — R — NH, 

Hydroxyazo (or " oxyazo ") compounds R — N = N — R — OH 

Azoxy compounds R — N — N — R 

\ / 
O 
Hydrazines R — NH — NH 2 

Hydrazones R — NH — N — C<^ 

/N 
Diazoimides R — Nil 

X N 



DERIVATIVES OF THE HYDROCARBONS. 12 3 



Oximes or isonitroso compounds ™^>C:=N— O — 

Nitroso compounds R — NO 

or R — N — NO 
R/ 

Mercaptans or thioalcohols R — S — H 

Sulphides or sulphur ethers R — S — R 

Sulphoxides ]| > S = O 

R^ ,^° 
O 

Sulphonium bases R — S — O — H 

R/ 

Sulphonic acids R — S0 2 — O — H 

Sulphochlorides . . . . R — S0 2 C1 

Sulphamides R — S0 2 NH 2 



Sulphones R^S 



Sulphinides R<£°>NH 



124 



ORGANIC CHEMISTRY. 



CHAPTER X. 



ALCOHOLS AND PHENOLS. 



CH3OH Methyl alcohol (Methanol) 
CH 3 CH 2 OH Ethyl alcohol (Ethanol) 
CH 3 CH 2 CH 2 OH Propyl alcohol (Propanoi-r) 
CH3CHOHCH3 Isopropyl alcohol (Propanol-2) 

CH 3 (CH 2 ) 2 CH 2 OH Primary butyl alcohol (Bu- 

tanol-i) 
CH.,CH 2 CHOHCH 3 Secondary butyl alcohol 

(Butanol-2) 

CH 3 > CH — CH 2° H Isobutyl alcohol (a-Me- 

thylpropanol-3) 
^2 3 > COH — CH 8 Tertiary butyl alcohol 

(2-Methylpropanol-2) 25 

CH 8 (CH 2 )j,CH 2 OH Normal amyl alcohol (Pen- 



Melting 
Point. 


Boiling 
Point. 


Sp. Gr. 





66° 


0.8142 (o°) 


— 112° 


78.3 


0.806 (o°) 





97-4° 


0.8205 (o°) 





82. i° 


0.798 (4 ) 





117° 


0.824 (o°) 





99° 


0.827 (o°) 



CH, 



tanol-i) 



cg 3 >CH — CH 2 CH 2 OH Isoamyl alcohol 

(2-Methylbutanol-4) 
CH 2 OHCH(CH,)CH 2 CH 3 Active amyl alcohol 

(2-Methylb'utanol-i) 

CH 3 (CH 2 ) 14 CH 2 OH Cetyl alcohol 



125.7" 
344° 



0.8 1 7 (0°) 

0.780 (26 ) 
0.830 (o°) 

0.825 (o°) 

0.833 (o°) 
0.817 (5o°) 



CH a = CH — CH 2 OH Allyl alcohol (i-Pro- 

penol-3) 
CH 8 CH = CH — CH 2 OH Crotyl alcohol (2-Bu- 

tenol-4) 

CH 2 = CH — CH 2 CH 2 OH i-Butanol-4 



CH 2 < £§2 > CHOH Cyclobutanol 

I 2 2 >CHOH Cyclopentanol 

CH 2 — CH 2 
CH 2 — CH 2 — CHOH 

I Cyclohexanol 

CH 2 — CH 2 — CHo 



96.6 0.871 (o°) 



IX 7 o 


0.873 (o°) 


ii3° 


0.864 (o°) 


123 





139° 


0.940 (21 ) 



160.5° 



ALCOHOLS AND PHENOLS. 



125 



CH 2 — CH 2 — CH 2 
CH 2 — CH 2 — CH 2 



> CHOH Cycloheptanol 



CH = C — CH 2 OH Propargyl alcohol (i-Pro- 
pinol-3) 



C 10 H 17 OH Borneol 

C 6 H 5 OH Phenol 
C 6 H 4 <gg* I ,-Cresol 
C 6 H4^q H 3 * ;«-Cresol 

QH4<oH 3 4 /"Cresol 

C G H 5 — CH 2 OH Benzyl alcohol (Phenmethylol) 

CH 
C 6 H 3 — OH 2 Carvacrol 

CH<g% 4 

/CH 3 1 

C 6 H 3 ^OH 3 Thymol 

CH<gHj-4 



OH 



CO 



OH 



a Naphthol 



Naphthol 



OH 



COD 



Anthranol 



CH 2 OH 

Glycol (Ethanediol) 
CH 2 OH 

CH 2 OHCHOHCH 2 OH Glycerol (Propanetriol) 
CHOH — CH 2 OH 

(d+l) Erythrol (Butane- 
CHOH — CH 2 OH tetrol) 

CHOH — CH 2 OH 

z-Erythrol (Butanetetrol) 
CHOH — CH 2 OH 

CHjOH(CHOH) 4 CHjOH Mannite (Hexane- 
hexol) 

CH 2 OH(CHOH) 4 CH 2 OH Dulcite (Hexane- 
hexol) 

CH,OH(CHOH) 4 CH 2 OH Sorbite (Hexane- 
hexol) 





184 


0.960(15°) 


17° 


H4°-ii 


:5° 0.971 (20°) 


!0 4 ° 


212° 


0.808 (210°) 


43° 


181. 5 


1.0597 (32.9 


30° 


190.8 


1.0578 (o°) 


4° 


202.8 


1.0498(0°) 


36° 


201 .8° 


1.0522 (o°) 




204.7° 


1 .0628 (o°) 


o° 


237° 


0.978 (20°) 



5I-5 1 - 



96° 



23 1.8° 0.940(65°) 



.224 ( 4 °) 



285° 



i63 -i 7 o c 



197- 
290° 



72- 
126° 

t66° 



.217 (4°) 



1.125(0°) 
(.262(17.5°) 



1.466(15°) 



126 ORGANIC CHEMISTRY. 

C 6 H 4<OH 2 Pyrocatechol (Phendiol i,2) io 4 ° 24o -2 4 s° 1-344 
C 6 H 4 <gg^ Resorcinol (Phendiol 1,3) "9° 276.5° 1.272(15°) 
C 6 H 4 <q2 I Hydroquinone (Phendiol 1,4) 169° 

The simplest derivatives of the hydrocarbons containing 
oxygen are the alcohols. They may be considered as 
derived from the hydrocarbons by the addition of an atom 
of oxygen, but their relation to the hydrocarbons is not so 
close as would appear from such a statement. 



ALCOHOLS, C w H 2n+2 0. 

Methyl Alcohol, CH 3 OH, (methanol). This is the first and 
simplest of all the alcohols. It is formed, along with many 
other products, by the destructive distillation of wood ; 
also by the destructive distillation of the residues from 
the spent liquors (vinasse) left when the molasses of beet 
sugar has been fermented for the production of alcohol. 
The crude product is separated from acetic acid by neutra- 
lization with milk of lime and distillation, and partly 
purified by fractional distillation. The still impure sub- 
stance obtained in this way, and known as " wood- 
alcohol," is used for burning, as a solvent for shellac in 
making varnish, and otherwise as a substitute for ordinary 
alcohol. These uses depend, economically, on the tax paid 
upon ordinary alcohol, as ethyl alcohol can be manufactured 
more cheaply than " wood spirit." Methyl alcohol is also 
used in the manufacture of many aniline dyes and for syn- 
theses of organic compounds. 

The " wood spirit " contains acetone and other impurities 
which cannot be removed by fractional distillation. The 
pure alcohol can be obtained by converting it into some 



METHYL ALCOHOL 1 27 

crystalline compound, the dimethyl ester of oxalic acid, 
(CH 3 ) 2 C 2 4 , being most suitable, or into some derivative 
which has a different boiling point, as methyl benzoate, 
C 6 H 5 C0 2 CH 8 . From the oxalic ester the alcohol can be 
regenerated by boiling with water or ammonia. 

(CH 3 ) 2 C 2 4 + 2NH3 + 2 H 2 = 2CH3OH + (NH 4 ) 2 C 2 4 - 

Methyl oxalate. 

Calcium chloride crystallizes with methyl alcohol much as 
it does with water, and the compound may also be used to 
purify the alcohol. Methyl alcohol boils at 66° and has a 

specific gravity or 0.7931 at . 

In general properties methyl alcohol resembles ordinary 
(ethyl) alcohol. When taken internally it produces intoxica- 
tion, and in larger doses acts as a poison. In solvent prop- 
erties it stands between ethyl alcohol and water, substances 
which dissolve in water dissolving more easily in methyl 
alcohol than in ordinary alcohol. 

Chemical Properties. — Sodium dissolves in methyl alcohol 
with evolution of hydrogen and formation of sodium methyl- 
ate. 

Na + CH 4 = CH 3 ONa + H. 

With the halogen acids it forms, more or less easily, mono- 
halogen derivatives of methane, and water. 

HI + CH 4 = CH 3 1 + H 2 0. 

* Methyl iodide. 

With other acids it yields compounds known as esters in 
which the hydrogen of the acid is replaced by methyl. 

2CH 4 + H 2 C 2 4 = (CH 3 ) 2 C 2 4 + 2H 2 

Dimethyl ester 
of oxalic acid. 



128 ORGANIC CHEMISTRY. 

These reactions demonstrate that one hydrogen atom of 

the alcohol is intimately associated with the oxygen atom, 

and that the same hydrogen atom conducts itself differently 

from the other three. These facts find their most natural 

expression in the formula, 

H 

I 
H-C-O-H. 

I 
H 

This formula is confirmed by the synthesis of methyl 
alcohol when its esters are boiled with water, or when 
methyl iodide is heated with water. 

(CH 8 ) 2 C 2 4 + 2HOH = 2 CH3OH + H 2 C 2 4 
CH 3 I + HOH = CH3OH + HI. 

Since other alcohols conduct themselves in the same man- 
ner, it is assumed that they all contain the hydroxyl group, 
and an alcohol is defined, structurally, as a hydrocarbon in 
which a hydrogen atom has been replaced by a hydroxyl 
group. In formulae and in their reactions the alcohols are 
analogous to the metallic hydroxides. An important differ- 
ence is found in the practically instantaneous reaction be- 
tween metallic hydroxides and acids, and the comparative 
slowness of the similar reaction between alcohols and acids. 
This is probably due to the greater dissociation of metallic 
hydroxides, most of the alcohols undergoing, apparently, 
very slight dissociation into the alkyl radical and hydroxyl ions. 
The reaction with sodium indicates that alcohols also dis- 
sociate into the group R-O- and hydrogen ions, but this 
dissociation, too, must be trifling, since the alcoholates are 
decomposed by a very small amount of water, even in the 
presence of large amounts of the alcohol. 



ETHYL ALCOHOL. 1 29 

By oxidation under appropriate conditions methyl alcohol 
gives formaldehyde, formic acid and carbonic acid. 



c< H 


/H 


/H 


/OH 


c'° 


C — H 


C— OH 


C-OH 


^q 


^0 


^O 


Methyl 


Formaldehyde. 


Formic 


Carbonic 


Carbon 


alcohol. 




acid. 


acid. 


dioxide. 



The structure of these compounds will be considered 
later. 

Effect of the Hydroxyl Group. — It should be noticed that 
the presence of the hydroxyl group in methyl alcohol com- 
pletely changes its character as compared with that of 
methane. While the hydrocarbons of the marsh-gas series 
are affected only by the most vigorous chemical agents, the 
alcohols are easily oxidized and react readily with acids and 
other substances. The presence of the oxygen decreases 
the stability of the molecule. Not only is this true in 
general, but that portion of the molecule containing the 
oxygen is most easily affected in the case of the homologous 
alcohols of the series, and so becomes the point of attack 
for oxidation and for the action of other agents. 

Ethyl Alcohol, C 2 H 5 OH (ethanol). Ordinary alcohol, or 
ethyl alcohol is, at present, always prepared, commercially, 
by the fermentation of solutions containing sugar. The two 
cheapest sources of such solutions are the molasses from 
which crystallizable sugars have been removed, and solu- 
tions prepared from substances which contain starch, espe- 
cially from Indian corn and potatoes. Liquors containing 
alcohol, such as wine, cider and perry, are obtained by the 
fermentation of the juices of grapes, apples and pears, which 
contain sugar, but these liquors are rarely used as a source 
of pure alcohol. 



13O ORGANIC CHEMISTRY. 

In the manufacture of alcohol from corn, which is most 
used in America, the grain is ground and put into steel 
boilers with water. It is then heated for about an hour to a 
temperature of 155 by means of steam under pressure. 
The pressure within the boiler is then rapidly reduced to a 
point considerably below atmospheric pressure. By this 
means the water within the starch granules is converted into, 
steam, and the covering of the granules is thoroughly 
ruptured, exposing the starch freely to the subsequent action 
of the diastase. The temperature, also, is rapidly reduced 
to 65°-7o°. One part of malt # is then added for about ten 
parts of the meal. At that temperature, the diastase con- 
verts the starch, (C 6 H 10 O 5 ) M , very rapidly into maltose, 
C 12 H 22 O u , (about 80 per cent), and dextrin, C 36 H 62 31 , (about 
20 per cent). The solution is then rapidly cooled, mixed 
with yeast, and diluted till a solution containing about ten 
per cent of saccharine matter, and at a temperature of 
i8°-2 2°, is obtained. The yeast (saccharomyces) causes the 
transformation of the maltose and of a part of the dextrin 
into alcohol and carbon dioxide. 

C 12 H 22 O n + H 2 = 4 C 2 H e O + 4 C0 2 . 

The reaction is exothermic, and the temperature of the 
solution rises io°— 12 during the three or four days of fer- 
mentation. For the successful growth of the yeast, there 
must be present, besides the saccharine matter, a small 
amount of nitrogenous material and of inorganic salts, 
especially phosphates and sulphates. 

Theories of Fermentation. — In the earlier theories of fer- 
mentation it was supposed (Liebig) that the action was due 

* Malt is prepared by moistening barley and leaving it in a warm place till it 
sprouts. The grain is then dried and the sprouts are removed. During germina- 
tion the barley develops a soluble nitrogenous compound called diastase. Diastase 
belongs to the class of bodies known as soluble ferments or enzymes (p. ). 



THEORIES OF FERMENTATION. 131 

to a catalytic effect of some substance present in the fer- 
menting solution, the general notion being that substances 
in a state of decomposition may, by their presence, cause 
the decomposition of other bodies. Later, the work of 
Pasteur established^ apparently, that the fermentation is 
inseparably connected with the life of the yeast. Recently 
it has been shown (Buchner), however, that by pressing 
yeast to remove the liquid which adheres to it, grinding it 
with sand to break the cell walls, and pressing it again, a 
liquid may be obtained which, after filtering through po- 
rous porcelain to remove all live yeast cells, will still cause 
a rapid transformation of glucose into alcohol and carbon 
dioxide. It seems, therefore, that the yeast contains a 
soluble ferment (enzyme), which transforms sugar, much as 
diastase transforms starch. This soluble ferment is called 
zymase, but it has not yet been isolated. Such action is 
called catalytic because the ferment itself appears to remain 
unchanged, and a very small amount of it may transform 
large quantities of the bodies affected. The chemical action 
involved is very poorly understood, but similar transforma- 
tions undoubtedly play a very important part in digestion 
and in other life processes. 

By the processes described above, a liquid is obtained con- 
taining about five per cent of alcohol by weight. This is 
subjected to fractional distillation. 

The " beer " is pumped continuously into a still, so con- 
structed with a series of shelves that the alcohol-free liquors, 
called " slop," run away at the bottom, while an alcohol of 60 
to 80 per cent distills continuously from the top. This crude 
alcohol is diluted and filtered through charcoal to remove 
corn oil, esters and other substances which impart to it a 
disagreeable taste and odor. It is then distilled a second 
time, and most of the alcohol is obtained with a strength of 



132 ORGANIC CHEMISTRY. 

90 to 95 per cent. Toward the end of this distillation a 
mixture of higher alcohols known as fusel oil passes over. 
This contains chiefly isoamyl alcohol with small amounts of 
isobutyl and propyl alcohols. The first portions of the dis- 
tillate also contain impurities, chiefly aldehyde, formed by 
the oxidation of a little of the alcohol as it passes through 
the charcoal. 

Absolute Alcohol. — Since the boiling point of pure alcohol 
is higher than that of an alcohol containing a small amount 
of water, it is impossible to obtain alcohol free from water 
by distillation alone. The mixture having the lowest boiling 
point contains 96 per cent of alcohol by weight, or 97.4 per 
cent by volume, and this mixture is the extreme limit which 
can be reached by fractional distillation. (J. Am. Chan. Soc. 
23, 463.) The last portions of water may be removed by 
boiling strong alcohol with lime, for some hours, in a flask, 
connected with an upright condenser. The removal of the 
last traces of water is extremely difficult, and even " absolute " 
alcohol usually contains one-half of a per cent of water. 

Ethyl alcohol boils at 78.3 and has a specific gravity of 

0.76326 f— % J. It solidifies at — 112 . 

Determination of Alcohol. — In mixtures containing noth- 
ing but alcohol and water, the amount of alcohol present is 
determined by means of the. specific gravity and by reference 
to tables. The specific gravity must be determined accurately 
by means of a picnometer, a Westphal balance, or a sensitive 
spindle. The alcohol must be brought to the temperature 
for which the table is constructed, or a temperature correction 
must be applied. In the case of liquors containing other 
substances than alcohol and water, the alcohol must be 
separated by distillation. The distillate is then usually made 



ABSOLUTE ALCOHOL 1 33 

up to the original volume and the specific gravity deter- 
mined. 

Physiological Effects. — Taken internally, ethyl alcohol 
lowers the temperature of the body 0.5 to 2 degrees. In 
moderate amounts it is mostly oxidized in the body and ap- 
pears to play essentially the same part as other foods in pro- 
ducing bodily warmth and energy. In larger amounts, or in 
concentrated form, it is a poison. 

" Proof spirit " in America is made the basis for taxation, 
and contains 50 per cent of alcohol, by volume. 

Uses. — Ethyl alcohol burns with a non-luminous, smoke- 
less flame, and hence is used for heating purposes in alcohol 
lamps. It dissolves very many organic substances, and is 
used in making varnishes, in preparing tinctures for medici- 
nal use, in the manufacture of ether, and in a great variety 
of ways in chemical factories and in laboratories. 

Chemical Properties. — In most of its chemical properties 
it resembles methyl alcohol. The formation of sodium ethy- 
late, C 2 H 5 ONa, or ethyl iodide C 2 H 5 I, and of esters con- 
taining the group C 2 H 5? as ethyl acetate, C 2 H 5 C 2 H 3 2 , can 
be satisfactorily explained only by assuming the structure, 
C 2 H 5 OH. In detail this becomes, 

H H 

H-C-C-O-H . 

1 1 
H H 

This view of its structure is further supported by a study of 
the oxidation products of ethyl alcohol. These are alde- 
hyde, C 2 H 4 0, and acetic acid, C 2 H 4 2 . 

Since sodium acetate, NaC 2 H 3 2 , gives methane, CH 4 , and 
sodium carbonate when heated with soda-lime, acetic acid 



134 ORGANIC CHEMISTRY. 

must contain a methyl (CH 3 ) group, and the same group 
must be present in acetaldehyde and in ethyl alcohol. 

Acetaldehyde, C 2 H 4 0, gives, on treatment with phosphorus 
pentachloride, ethylidene chloride, CH 3 CHC1 2 , and hence 
probably contains an oxygen atom which is doubly united 
with a carbon atom. 

/yO /CI 

VH 



CH 3 -C : -f= PC1 5 = CH 3 -C-C1 + POCI3. 



It is noticeable that in the oxidation of ethyl alcohol to 
aldehyde and acetic acid the portion of the molecule attacked 
is that portion already containing the hydroxyl group. Since 
ethyl alcohol is a saturated body, we may suppose that oxy- 
gen enters between a hydrogen and a carbon atom giving, at 

/OH 
first, a compound CH 3 — C — OH. Compounds of this char- 

^H 
acter, having two hydroxyl groups combined with a single 
carbon atom, are unstable, or, in most cases, incapable of ex- 

istence. The aldehyde, CH 3 — C , which results on loss 

of water, takes, on further oxidation, a second oxygen atom 

between the carbon and hydrogen atoms, giving acetic acid, 

//O 
CH 3 -C N Q H 

The oxidation products of ethyl alcohol here given are 
typical for all alcohols containing the group -CH 2 OH. 

Normal Propyl Alcohol, CH 3 -CH 2 -CH 2 OH, (propanol-i), 

is found in small amount in fusel oil. Its structure is es- 
tablished by a study of its oxidation products, which are 

//® 
propionic aldehyde, CH 3 CH 2 C 5 and propionic acid, 

> H 

CH 3 CH 2 C ( . (See also p. 62.) 



TERTIARY BUTYL ALCOHOL. 135 

ptJ TT 

Isopropyl Alcohol, _ TJ 3 > C < ^^ , (propanol-2), is pre- 
Cxlg (Jrl 

pared by boiling isopropyl iodide, CH 3 CHICH 3 , with water. 

It has also been prepared by the reduction of acetone, 

CHgCOCHg, by means of sodium amalgam. The structure 

is established by the preparation from acetone and by the 

fact that acetone gives a mixture of acetic and formic acids 

by oxidation. 

Isopropyl alcohol is also called secondary propyl alcohol 

and is the simplest of the secondary alcohols. The sec- 

TT 

ondary alcohols contain the group =C< , and give, on 

oxidation, ketones, containing the group =C = O, and then 
acids with a smaller number of carbon atoms. 

There are four butyl alcohols possible, and all of them are 
known. 

Primary Normal Butyl Alcohol, CH 3 CH 2 CH 2 CH 2 OH, (bu- 

PIT 

tanol-i), and Primary Isobutyl Alcohol, 3 >CH-CH 2 OH, 

CH 3 

methyl— 2-propanol-i), give, by oxidation, aldehydes and 

acids, as do all primary alcohols. 

Secondary Normal Butyl Alcohol, CH 3 CHOHCH 2 CH 3 , 
(butanol-2), gives butanone, CH 3 COCH 2 CH 3 , by oxidation 
and, on further oxidation, acetic acid. 

CH 3 \ 
Tertiary Butyl Alcohol, CH 3 — COH, (metyl-2-propanol-2), 
CH 3 / 
gives acetone, CH a COCH 3 , and carbon dioxide by oxidation. 
The compound is usually called trimethyl carbinol, the name 
signifying that it is carbinol (methyl alcohol) in which three 
hydrogen atoms have been replaced by methyl. 



136 ORGANIC CHEMISTRY. 

The structure of these alcohols is established by their con- 
duct when oxidized. As is apparent from the illustrations 
given, primary alcohols contain the group CH 2 OH combined 
directly with a single carbon atom and give, by oxidation, al- 
dehydes and acids containing the same number of carbon 
atoms as the alcohol. Secondary alcohols contain the gro>ip 
> CHOH combined directly with two carbon atoms and give, 
by oxidation, ketones, and then an acid or acids with a smaller 
number of carbon atoms. 

Tertiary alcohols contain the group =COH combined di- 
rectly with three carbon atoms, and cannot be oxidized with- 
out loss of carbon. 

Eight amyl alcohols, C 5 H u OH, are theoretically possible, 
and all have been prepared.* The only ones which have 
especial interest are the isoamyl alcohol, 

™ 3 > CH-CH 2 CH 2 OH, 

(methyl-3-butanol-i) and active amyl alcohol, 

CH3 "™ 2 >CH-CH 2 OH, 

(methyl-2-butanol-i). Each of these is found in fusel oil, 
the pentyl alcohols of fusel oil consisting of 80-90 per cent 
of the first mixed with 1 0-2 o per cent of the second. If the 
mixture is treated with hydrochloric acid gas and warmed, 
the isoamyl alcohol is converted into amyl chloride, C 5 H U C1, 
more easily than the active amyl alcohol. In this manner 
a left-handed alcohol has been obtained having a rotation 
[a]/j= — 5-90°. (See p. 47.) The active alcohol has never 
been prepared artificially and no experiments furnishing 
direct evidence of its structure have been made. 

* The student will find it profitable to write the formulae and official names of these 
eight alcohols, and also to state their oxidation products. 



OPTICAL ACTIVITY. 



137 



Optical Activity. — A careful study of a very large number 
of active organic substances has shown, however, that in all 
cases where the structure of such substances has been de- 
termined, they contain at least one carbon atom which is 
combined with four different atoms or groups. Such a car- 
bon atom is called* an asymmetric carbon atom, since, if we 
consider the atoms or groups as situated in the direction of 
the axes of a tetrahedron with regard to the center of this 
carbon atom, two arrangements are possible. The two forms 
are related to each other in the same manner as an object 
and its image in a mirror. The relationship will be clear 
from a study of the accompanying figures. 




Fig. 25. 

In crystallography two crystals related in this manner are 

said to be enantiomorphic. 

Now, of the four possible primary amyl alcohols, only 

iii 1 CH CHn H 

methyl-2-butanol-i, 3 ^ TT > C < 



CR 



CH 9 OH 



contains an 



asymmetric carbon atom. It is assumed, therefore, that the 
active amyl alcohol possesses this structure. 

Every active body may, theoretically, exist in at least two 
forms, a right-handed and a left-handed body. The right- 
handed body causes exactly the same degree of rotation to 
the right that the left-handed body does to the left. A mix- 
ture of equal parts of the two is inactive, and is often spoken 
of as a third form. The three forms are distinguished by 
the prefixes d, ( for dextrd) /, (for laevo) and i (for inactive). 



138 ORGANIC CHEMISTRY. 

The inactive mixture is also often called the racemic form, 
because the mixture of d- and /-tartaric acid, called racemic 
acid, is the first compound in which this relationship was 
discovered. 

Enantiomorphic forms are identical in all of their physical 
and chemical properties except in their conduct toward 
polarized light, toward other optically active bodies, toward 
certain bacteria and ferments, and, in a few rare instances, 
in regard to their crystalline forms. A racemic form, how- 
ever, often differs very considerably in its properties from its 
active components. 

The synthesis from inactive materials of any compound 
having an asymmetric carbon atom always produces the 
racemic form ; that is, a mixture is produced having the 
right-handed and left-handed bodies present in equal pro- 
portion. Three general methods have thus far been practi- 
cally applied to the separation of such mixtures. 

Separation of Racemic Compounds into their Components. — 

1. In a very few instances the two active forms may be sepa- 
rated by crystallization. Thus a solution of the sodium 
ammonium salt of racemic acid, (NaNH 4 C 4 H 4 6 ) 2 -|-2H 2 0, 
deposits, on evaporation, at temperatures below 2 8°, two 
kinds of crystals which may be separated mechanically. 
These crystals are enantiomorphic, and one set gives */-tar- 
taric acid and the other /-tartaric acid. 

2. Compounds of racemic bodies with active substances 
often deposit the compound with one of their active constitu- 
ents more easily than with the other, and the two optical 
isomers may then be separated by fractional crystallization. 
The active bodies most often used for such purposes have 
been strychnine, cinchonine and brucine for acids, and tar- 
taric acid for bases. 



VINYL ALCOHOL 1 39 

3. It has been found in many cases that micro-organisms 
cause the fermentation and destruction of one of the isomers 
in a racemic mixture, while the other is left unaltered or is 
little affected. As some one has put it, the organisms seem 
to have a better appetite for a right-handed body than for a 
left-handed one, or'vice-versa. At basis, this method of sepa- 
ration is probably essentially the same as the second method, 
the peculiar action of the organisms being, doubtless, due to 
active compounds which they contain. 

Pasteur effected the first separation of a racemic com- 
pound (racemic acid itself) into its optically active constitu- 
ents, and he discovered all three of the general methods 
which are used in such separations. {Ann. Chim. Phys. 
[3] 24, 442 ; 28, 56 ; 38, 437. Pasteur's " Researches on 
the Molecular Asymmetry of Natural Organic Bodies," 
Alembic Club Reprints No. 14.) 

A considerable number of alcohols of this series contain- 
ing a larger number of carbon atoms are known, but there 
are no new facts of such general interest as to require their 
mention here. 

Alcohols of the Ethylene Series, C n H 2n _ 1 OH. 

As methylene, CH 2 , the hypothetical first member of the 
ethylene series, appears to be incapable of a separate exis- 
tence because of its tendency to polymerize or combine with 

TT 

itself, so the corresponding alcohol, C < , is entirely 

. (J — H. 

unknown. 

TT 

Vinyl Alcohol, CH 2 =C< (ethenol), apparently exists 

O— M 

in small amount in commercial ether, but it has never been 

prepared in a pure condition. Reactions which would 

naturally give vinyl alcohol always lead to the formation of 



140 ORGANIC CHEMISTRY. 



/ it 

aldehyde, CH 3 C . , instead. It seems that the vinyl alco- 
hol at first formed adds water, giving the compound, 

/H 
CH 3 C — O-H , 
\0-H 

and the latter loses water again with the formation of alde- 
hyde. Transformations of -this sort evidently play an im- 
portant part in the case of many compounds with a similar 
grouping, and have been a fruitful source of confusion 
and controversy. (See acetacetic ester and the alkyl nitro 
compounds.) 

Allyl alcohol, CH 2 =CH-CH 2 OH (propenol-i), is formed 
when glycerol is heated with oxalic acid. The oxalic acid 

decomposes at first into formic acid, H — C , and car- 

bon dioxide. The formic acid reacts with the glycerol, 

CH 2 OH 

I 
CHOH, to give an ester, diformin^ 

I 
CH 2 OH 

CH 2 -0-<2 

CH-O-C^ an d the latter finally 
, \H' 

CH 2 -OH 

decomposes, giving- formic acid, carbon dioxide and allyl 
alcohol. In an important sense the allyl alcohol may be 
considered as a reduction product of glycerol, oxalic or 
formic acid being the reducing agent. 



ALLYL ALCOHOL. 141 

Allyl alcohol boils at 9 6. 6° and has a disagreeable odor. 
As a primary alcohol it may be oxidized to the aldehyde, 

acrolein, CH 2 = CH — C / , and to the acid, acrylic acid, 
\ H 



CH 2 = CH — C; ,^ TT , but, on account of its unsaturated 



\0--H ; 

character, much greater care is required for these operations 
than in the case of saturated alcohols. As an unsaturated 
compound, on careful oxidation with potassium permanganate 
it takes up two hydroxyl groups and is converted into 
glycerol. When treated with bromine, it is converted into 
2.3 dibrom-propanol-i, CH 2 Br CHBr CH 2 OH. With phos- 
phorus tribromide it gives allyl bromide, CH 2 = CH — 
CH 2 Br, and the latter takes up hydrobromic acid, giving 
trimethylene bromide, CH 2 BrCH 2 CH 2 Br, or 1.3 dibrom- 
propane. 

The isomeric unsaturated alcohol, propenol-2, 



CEL= C 



OH 



\CH 3 



or /?-allyl alcohol, appears to be incapable of existence, for 
reasons similar to those which cause vinyl alcohol to pass 
over into aldehyde. In the same manner /3-allyl alcohol 
goes over into acetone, CH 3 — CO — CH 3 . On treatment 
with metallic sodium, however, acetone gives a compound 

having, apparently, the structure X C — ONa, which is 

to be looked upon as a derivative of the unsaturated alcohol. 
(Freer, Aim. Chem. (Liebig), 278, 116; Am. Chem. Jour., 15, 

582.) 

Many alcohols of this series containing a greater number 
of carbon atoms are known, but need not be considered 
here. 



142 ORGANIC CHEMISTRY. 

Cyclic Alcohols. ■ — Several cyclic alcohols which are iso- 
meric with the unsaturated alcohols of this series are known. 
As with the cyclic hydrocarbons, those containing rings of 
five and six carbon atoms are most stable and of greatest 

CH 2 -CH 2 
interest. Cyclopentanol, | > CHOH, has already 

CH 2 -CH 2 
been referred to as a step in the preparation of cyclopen- 
tane (p. 84). 

ALCOHOLS C n H 2M _ 2 0. 

The alcohols of most interest having this general formula 
are a considerable number of compounds closely related to 
camphor and the terpenes. 

Borneol, C 10 H 18 O, is formed by the reduction of camphor, 
C 10 H 16 O, by means of sodium and alcohol. The three forms, 
d-, /-, and /-borneol, have been prepared. It has the 
properties of a saturated secondary alcohol, and must, there- 
fore, contain two rings of carbon atoms. Its structure 
follows from that of camphor (p. 195). 



PHENOLS AND ALCOHOLS, C n H 2w _ 6 0. 

Phenol, or Carbolic acid, C 6 H 5 OH. Derivatives of benzene 
and its homologues in which a hydrogen atom of the 
nucleus is replaced by hydroxyl show properties so dif- 
ferent from those of the alcohols of the methane and ethy- 
lene series that they are given a distinctive name and are 
called phenols. The simplest compound of the class is 
phenol, C G H 5 OH, or, as it is commercially known, carbolic 
acid. It is one of the constituents of coal-tar, and is 
obtained partly by fractional distillation, partly by solution 



PHENOLS AND ALCOHOLS. 1 43 

in sodium hydroxide, and reprecipitation by sulphuric 
acid. 

When pure, phenol is a colorless solid which melts at 43 , 
and boils at 183 . It dissolves in 20 parts of water at 17 . 
It also dissolves a small amount of water, the solution being 
liquid ; hence, if shaken with less than 20 parts of water at 
1 7 , the mixture will separate, on standing, into an upper 
layer containing about five per cent, and a lower layer con- 
taining about seventy-five per cent of phenol. 

One of the most marked differences between phenol and 
the alcohols of the marsh-gas series is in their conduct 
toward alkalies. While alcoholates, such as sodium ethylate, 
C 2 H 5 ONa, can be easily obtained by dissolving metallic 
sodium or potassium in the anhydrous alcohols, these com- 
pounds are instantly decomposed by water with the forma- 
tion of the hydroxide of the metal and the regeneration of 
the alcohol. Sodium phenolate, C 6 H 5 ONa, on the contrary, 
can be prepared by dissolving phenol in a solution of sodium 
hydroxide and evaporating to dryness. Phenol is precipi- 
tated from its alkaline solution, however, even by carbonic 
acid. If other hydrogen atoms of phenol are replaced 
by negative groups, the resulting substitution products are 
more strongly acid. Thus trinitro-phenol, or picric acid, 
C 6 H 2 (N0 2 ) 3 OH, is a sufficiently strong acid to decompose 
carbonates. 

In accordance with the generally accepted theory of solu- 
tions, these facts mean that the alcohols of the marsh-gas 
series dissociate in the pure state, or in aqueous solution, 
with the formation of fewer hydrogen ions than does water 
itself, and that phenol undergoes less, while picric acid under- 
goes more dissociation than carbonic acid. These facts can 
be given an accurate quantitative expression by means of the 
conductivity constants (see p. 49). 



144 ORGANIC CHEMISTRY. 

Picric acid,* K— 

Acetic acid, A"— 0.0018 

Carbonic acid, ^=0.0000304 

Hydrogen sulphide, ^=0.0000057 

Hydrocyanic acid, K— 0.0000013 

Phenol, AT— 0.00000013 

In a decinormal solution (i.e., v = 10.) the percentage dis- 
sociation is : 

Hydrochloric acid 91.4 

Acetic acid 1.3 

Carbonic acid 0.174 

Hydrogen sulphide 0.075 

Hydrocyanic acid 0.0 n 

Phenol 0-0037 

The conductivity of pure ethyl alcohol has not been de- 
termined. It is undoubtedly very much less than that of 
water. The conductivity constant for acetic acid is given 
for comparison. 

If we look for the reason for the acid character of phenol, 
two explanations suggest themselves. One is that with the 
loss of hydrogen the " positive " or basic character of the 
group C 2 H 5 of ethyl alcohol or C 6 H n of cyclohexanol 
(C 6 H u OH) passes into a comparatively "negative " or acid 
character for the group C 6 H 5 . This view is supported by 
the conduct of picric acid, where the replacement of hydro- 
gen by negative groups greatly increases the acid character. 
The other explanation is that, if we assume Kekule's formula 
for benzene as correct, the acid character of the hydroxyl is 
due to the double union of the carbon atom bearing it with 
another carbon atom of the ring. In support of this view it 
may be said that no carbon compound containing a hydroxyl 
group with acid properties is known in which the carbon 

* The conductivity of picric acid is of the same order as that of the strong mineral 
acids, and a constant cannot be given. 



CHEMICAL CHARACTER OF PHENOLS. 1 45 

atom combined with the hyclroxyl is not doubly united with 
some other atom. It is very likely that both of the factors 
mentioned are effective in the case of phenol. 

Chemical Character of Phenols. — Just as the introduction of 
hydroxyl into hydrocarbons of the marsh-gas series produces 
compounds which are easily oxidized and readily acted upon 
by other reagents, so phenol gives substitution products more 
easily, and is in other respects a much less stable compound, 
than benzene. Strong nitric acid is required to prepare 
nitrobenzene, C 6 H 5 N0 2 , from benzene, while dilute nitric 
acid will convert phenol into a mixture of ortho- and para- 

ATT 

nitrophenol C 6 H 4 < , and trinitrophenol, C c H 2 (N0 2 ) 3 OH 

is easily prepared. 

In alkaline solutions phenols are especially unstable, and 

/ONa 1 
easily oxidized. Sodium pyrogallate, C 6 H 3 — ONa 2, absorbs 

^ONa 3 
oxygen so rapidly that its solution is used for quantitative 
determinations in gaseous mixtures. 

By distillation with zinc dust, phenol is converted into 
benzene. 

By means of phosphorus pentachloride or pentabromide, 
the hydroxyl of phenol can be replaced by chlorine or 
bromine. 

C 6 H 5 OH + PC1 5 = C 6 H 5 C1 + POCl 3 + HC1. 

Monochlor- 
benzene. 

The reaction takes place with some difficulty, and the 
yield is poor owing to the formation of triphenyl phosphate, 
PO(OC 6 H 5 ) 3 . 

By the action of chlorine on a solution of phenol in sodium 



146 ORGANIC CHEMISTRY. 

hydroxide it is converted into trichlorcyclopentenediol car- 
boxylic acid, C 6 H 5 C1 3 4 , probably through the following 
stages : 

OH OH 

I I 

C C CO 

# \ // \ / \ 

CH CH CC1 CC1 CC1 2 CO 

I II -> I II- r* I I 

CH CH CH CH . CH CH 2 

% / ^ / ^ / 

CH CC1 CC1 

CO OH C0 o H C0 2 H 

I I I 

CCLH CO CCU-C-OH CC1 2 -C-0H 

-> I I -> I I -> I I 

CH CH 2 CH CH 2 COH CH 2 

CC1 CC1 CC1 

These transformations are of especial interest because a 
ring of six carbon atoms is changed into one containing five 
carbon atoms. Similar transformations, which occur both 
ways with rings containing five, six and seven carbon atoms, 
have been observed in a number of other cases, and a 
study of such transformations seems destined to be of 
increasing importance. 

Phenol may be prepared by fusing potassium benzene-sul- 
phonate with caustic potash, or by treating aniline sulphate 
with nitrous acid (or sodium nitrite) and boiling the resulting 
benzene diazonium sulphate with water. 

C 6 H 5 S0 2 OK + KOH = C 6 H 5 OH + K 2 S0 3 . 

Potassium benzene 
sulphonate. 



CRESOL. 147 



(C 6 H 5 NH 2 ) 2 H 2 S0 4 + 2 KN0 2 + H 2 S0 4 = 

Aniline sulphate. /C 6 H 5 N - \ S0 4 + K 2 S0 4 + 4 H 2 0. 

1 ft I 

Benzene diazonium 
sulphate. 

(C 6 H 5 N 2 ) 2 S0 4 + 2 H 2 - 2 C 6 H 5 OH + H 2 S0 4 + N 2 . 

Both methods are general, and are especially useful in 
preparing homologues of phenol, and also in preparing 
hydroxyl derivatives of naphthalene, anthracene, etc. Phenol 
is a valuable disinfectant, if applied in not too dilute a solu- 
tion. Its vapor is worthless for this purpose, however. 

. PTT 

Cresol, or Hydroxy toluene, C 6 H 4 3 , exists, in accord- 

ance with the theory, in three forms. These are found in 
coal-tar and in wood-tar. Creosote, obtained from wood- 
tar, contains both phenol and a mixture of the cresols. It is 
very difficult to prepare the individual cresols from tar, and 
they are prepared, practically, from toluene-sulphonic acids, 

QH 4 ^ ,orthetoluidines(aminotoluenes),C 6 H 4 ATrT 3 , 

\ o(J 2 (Jxi \ JNrl 2 

by methods exactly similar to those given under phenol. 

If a pure ortho, meta, or para compound is used, pure 

o-, m- or p-cresol can be obtained. Cresols and other 

phenols may be obtained by distilling hydroxy acids with 

lime. 

C 6 H 3 -OH + CaO = C 6 H ' ™ 3 + CaC0 3 . 
\C0 2 H XUM 

Hydroxy-toluic acid. 

This method of preparation is often important as a means 
of determining the structure of hydroxy acids, or of other 
compounds (as amino acids, sulphonic acids, etc.) which can 
be readily converted into hydroxy acids. 



148 



ORGANIC CHEMISTRY. 



Benzyl * alcohol, C 6 H 5 CH 2 OH, is as radically different 
from the phenols as the difference in structure suggests. 
While the halogen derivatives of benzene and its homo- 
logues which contain the halogen in the nucleus, can be 
converted into phenols only by fusion with caustic potash, 
benzyl chloride is converted into benzyl alcohol by boiling 
with water, or with water and lead oxide. 

C 6 H 5 CH 2 C1 + HOH = C 6 H 5 CH 2 OH + HC1. 

In its chemical conduct benzyl alcohol resembles, almost 
perfectly, the primary alcohols of the marsh-gas series. 
What transformations will illustrate these properties ? 

Carvacrol and Thymol, C 10 H 13 OH, are derivatives of cy- 
mene, with the following formulae : 



OH 





C-H 3 — CH — C^Hg 

Carvacrol . 



OH 



CH 3 -CH-CH a 

Thymol. 



The structure is established by the facts that each can 
be converted into cymene, that each has the properties 
of a phenol, and must therefore contain the hydroxyl 
group in the nucleus, and that carvacrol gives o-cresol 
and propylene on heating with phosphorus pentoxide. 

Carvacrol is of interest because of its preparation from 
camphor. Thymol has similar germicidal properties to 
phenol, but is less poisonous and can be taken internally. 



* The group C 6 H 5 CH 2 — is called benzyl, the group CH 3 C 6 H 4 — , tohiyl or tolyl. 



ALCOHOLS CONTAINING TIVO HYDROXY L GROUPS. 1 49 



PHENOLS, C B H 2H _ 12 and C w H 2H _ 18 0. 

o-Naphthol and /?-Naphthol may be prepared, the first by 
treating a-naphthylamine with nitrous acid, the* second by 
fusing /^-naphthalene sulphonic acid, 

SOoOH 



with caustic potash. The /?-naphthol is more easily ob- 
tained, and is used in surgery and medicine as an antiseptic. 
Three phenols derived from anthracene are possible. 
Without any logical reason, those in which the hydroxyl is 
combined with one of the outer nuclei are called aiittwols, 
while the one in which the hydroxyl is combined with one 
of the central carbon atoms is called anthranol. Anthranol, 

COH 
C 6 H 4 < I > C 6 H 4 , is readily obtained by the reduction of 

CH 
anthraquinone. 

ALCOHOLS CONTAINING TWO OR MORE 
HYDROXYL GROUPS. 

In most cases alcohols containing two hydroxyl groups 
combined with the same carbon atom cannot exist as inde- 
pendent compounds. Reactions which would give rise, 
naturally, to the formation of such compounds, give alde- 
hydes or ketones instead. Thus benzaldehyde, C 6 H 5 C 

\ H 

is formed by heating benzylidene chloride, C 6 H 5 -CHG1 2 
with water; and acetone, CH 3 — CO — CH 3 , is formed when 
2.2-dichlorpropane, CH 3 — CC1 2 CH 3 is heated with water. 



150 ORGANIC CHEMISTRY. 

Only in a few unusual cases, and apparently always when the 

group containing the two hydroxyl groups is combined with 

a strongly negative group or groups, do exceptions to this 

general rule occur. Thus chloral hydrate has probably the 

structure, * ^ TT 

/OH 

CC1 3 -C-0H, 

\H 

and mesoxalic acid the formula, 

C0 2 H 

' /OH 
I \0H* 

C0 2 H 

In accordance with what has been said, the first stable 
alcohol having two hydroxyl groups contains also two carbon 
atoms ; the first one with three hydroxyl groups contains 
three carbon atoms, and so on for other alcohols containing 
several hydroxyl groups. 

CH 2 OH 
Glycol, | (ethandiol), may be prepared by boiling 

CH 2 OH 

ethylene bromide with a solution of potassium carbonate. 

CH 2 Br CH 2 OH 

| + K 2 C0 8 + H 2 = | +2 KBr + C0 2 . 

CH 2 Br CH 2 OH 

The diacetic ester of glycol can be prepared by heating 
ethylene bromide with silver acetate. 

CH 2 Br CH 2 .C 2 H 3 2 

| + 2 C 2 H 3 2 Ag =| +2 AgBr. 

CH 2 Br CH 2 .C 2 H 3 2 



GLYCOL 151 

The ester may be saponified with caustic potash. 

CH 2 C 2 H 3 2 CH 2 OH 

I +2KOH- I + 2 C 2 H 3 2 K. 

CH 2 C 2 H 3 2 CH 2 OH 

Glycol is a colorless liquid with a sweet taste. It boils at 
1 9 7 , and solidifies in a freezing mixture. Its chemical con- 
duct corresponds to its structure as a primary alcohol. From 
this structure we should expect the following series of oxida- 
tion products : 

CH 2 OH C '° C f 2 C (OH C 'g • 

' ->" -*OoS' OH ^Oo 

CH 2 OH CH 2 OH C ^ f- -OH C^^ H 

Glycol. Glycolic Glyoxal. Glyoxylic Oxalic 

aldehyde. acid. acid. 

C -OH | 

I 
CH 2 OH 

Glycolic acid. 

All of these substances are known, but some of them have 
not been prepared by direct oxidation of glycol, and all of 
them can be more easily prepared by other methods. 

The official names for these compounds are : ethanediol, 
ethanolal) ethanedial, ethanolic acid, ethanediolic acid, ethane- 
diacid. 

Glycol forms alcoholates in which one or both of the 
hydrogen atoms of the hydroxyl groups are replaced by 
alkali metals. The sodium glycolate, C 2 H 4 2 Na 2 , crystallizes 
with ioH 2 0, from which it seems that glycol is more acid in 
character than ethyl alcohol (see p. 143). 

With acids glycol forms esters in which one or both of 



152 ORGANIC CHEMISTRY. 

the alcoholic hydrogen atoms may be replaced by the acyl 
group. These may be prepared by the use of the silver or 
potassium salts of the acid (see above), or by the action 
of the acid chloride on glycol. 

CH 9 OH O CH„0 . C 2 H 3 

| -f 2 CH 3 -Cf =| +2HCI. 

CH 2 OH X C1 CH 2 O.C 2 H 3 0. 

Acetyl chloride Di-acetyl derivative 

of glycol. 

Propylene glycol, or 1,2 Propanediol, CH 2 OH, CHOH, CH 3 , 
and Trimethylene glycol, or 1.3 Propanediol, CH 2 OH, CH 2 , 
CH 2 OH are both known. The latter has been found in 
impure glycerol, and appears to have been formed by the 
reduction of glycerol under the influence of bacteria. (/. 
Am. Ch. Soc. 17, 890.) 

Glycerol, # or Propanediol, 

CH 2 OH 

I 
CHOH , 

I 
CH 2 OH 

occurs combined with acids in the natural fats, the most 
common compounds being stearin, C 3 H 5 (C 18 H 35 2 ) 3 , found in 
tallow and lard ; palmitin, C 3 H 5 (C 16 H 33 2 ) 3 , found in palm- 
oil and lard ; and olei'n, C 3 H 5 (C 18 H 33 2 ) 3 , found in olive-oil 
and lard. When the fats are boiled with aqueous or alco- 
holic solutions of potassium or sodium hydroxide, they are 
sap07iified or decomposed with the formation of glycerol and 
the metallic salt of the organic acid. The latter is a soap. 

C 3 H 5 (C 18 H 35 2 ) 3 + 3 NaOH = C 3 H 5 (OH) 3 + 3 C 18 H 35 2 Na. 

Stearin. Glycerol. Sodium stearate. 

* The scientific name is used, though it will be long before " glycerine " will be dis- 
placed in common usage. 



GL YCEROL. I 5 3 

Commercially the fat is saponified by heating it with 
water and four per cent of its weight of lime in an auto- 
clave. The acids obtained are used as commercial " stear- 
ine " in the manufacture of candles, and for other purposes, 
while the aqueous solution containing the glycerol is dis- 
tilled with superheated steam. 

Glycerol has been prepared synthetically by heating 1.2.3 
tribrompropane with silver acetate and saponifying the 
triacetin, C 3 H 5 (C 2 H 3 2 ) 3 , which is formed, with barium 
hydroxide. 

It has also been prepared by oxidizing allyl alcohol with 
potassium permanganate. 

CH 2 CH 2 OH 

II I 

CH • + + H 2 = CHOH 

I I 

CH 2 OH CH 2 OH 

Pure glycerol is a very viscous sweet syrup, having a 
specific gravity at 15 of 1.265. It solidifies slowly at a 
low temperature, and the crystals melt at 17 . It boils 
with slight decomposition at 290 . Under a pressure of 
50 mm. it boils at 210 ; under 12.5 mm., at 180 . 

The chemical conduct of glycerol is in strict accor- 
dance with its structure. The most interesting of its 
oxidation products are glyceric acid (propaiiediolic acid), 
CH 2 OH-CHOH-C0 2 H, tartronic acid (propanoldiacid*), 

C0 2 H 



CHOH <COH' 



and mesoxalic acid {propanediol diacid), 

CQ 9 H 



C (° H >*<C0 2 H 



154 ORGANIC CHEMISTRY. 

The last cannot be further oxidized without loss of 

carbon. 

CH 2 -0-N0 2 

I 
Glycerol Trinitrate, CH — O — N0 2 , is prepared by run- 

I 
CH 2 -0-N0 2 

ning glycerol slowly into a mixture of strong sulphuric and 
nitric acids, the temperature being carefully controlled. It is 
known commercially as nitroglycerine. It solidifies at — 20 . 
At ordinary temperatures it is a light yellow liquid with a 
specific gravity of 1.6009 at 15 . In small quantities it 
can be burned quietly. It explodes on concussion, with a 
detonating cap, or when heated to 250 . Nitric oxide, car- 
bon dioxide, water and nitrogen are formed by the detona- 
tion. The poisonous character of the nitric oxide sometimes 
causes trouble when nitroglycerine or dynamite is used for 
blasting in confined spaces. Dy7iamite is prepared by mix- 
ing nitroglycerine with infusorial earth (kieselguhr), sawdust, 
or the pith of corn-stalks, the most powerful forms contain- 
ing 75 per cent of nitroglycerine. A mixture containing 93 
per cent, of nitroglycerine and 7 per cent of nitrocellulose 
(gun-cotton) forms a semi-solid, gelatinous mass known as 
explosive gelatine. Nitroglycerine is also used in medicine 
as a heart stimulant. It is a powerful poison. 

Erythrol, CH 2 OH,CHOH,CHOH,CH 2 OH.— Glycol and 
glycerol cannot exist in optically active forms, since neither 
contains an asymmetric carbon atom. Erythrol, however, 
contains two such atoms. At first thought this should 
give, by the various possible combinations, four active forms 
and two racemic mixtures. The active forms on this sup- 
position may be written as follows : 



ERYTHROL 155 

CH 2 OH CH 2 OH CH 2 OH CH 2 OH 

III I 

H-C-OH H-C-H H-C-OH HO-C-H 

III I 

HO-C-H H-C-OH H-C-OH HO-C-H 

1 A ' ' 

CH 2 OH CH 2 OH CH 2 OH CH 2 OH 

a?- Erythrol. /-Erythrol. * — 



(d-{- 1) Erythrol (m. p. 72 ). 



i'-Erythrol (m. p. 126 ). 



A little examination shows, however, that the third and 
fourth forms, above, are inactive by an internal compensa- 
tion, since the two halves of the molecule are identical and 
turned in opposite directions. A study of the models also 
shows that these two forms are identical, and that the differ- 
ence in writing the formulae does not correspond to any real 
difference in structure. The first and second formulae, on 
the other hand, represent right-handed and left-handed forms 
which may actually exist. From the above there should be 
two active forms of erythrol, an inactive, racemic form re- 
sulting from the combination of the first two, and an inactive 
form which is inactive by internal compensation. 

No active form of erythrol has been prepared, but two 
forms are known, one melting at 72 , the other at 12 6°. If 
1,3 butadiene, CH 2 = CH — CH = CH 2 , is treated with 
bromine, the bromine atoms appear to add themselves to the 
end carbon atoms, while a double union is formed between 
the two central atoms. The compound at first formed is 
unstable, but on warming to ioo° two stable forms result. 
If we assume that so long as carbon atoms are united singly 
a free rotation at the point of union is possible, but that 
when doubly united such free rotation becomes impossible, 
the following formulae may be assigned to the two dibrom- 
ides : 



1 5 6 




ORGANIC CHEMISTRY. 

CH Br He — *CH 2 Br 




CH 2 Br BrH 2 C 
Fig. 26. 

Isomerism of this kind is called geometrical isomerism, or 
stereoisomerism, because the explanation given involves a 
discussion of the actual arrangement of the atoms and groups 
in space. The fundamental conception in this explanation 
is closely related to the doctrine of the asymmetric carbon 
atom, which is that the four atoms or groups, combined with 
any given carbon atom, naturally arrange themselves in ap- 
proximate, or, if the groups or atoms are identical, in abso- 
lute symmetry about the center of that atom. In figures the 
carbon atom is sometimes represented in the form of a tetra- 
hedron, as a matter of convenience, but it must not be sup- 
posed that any satisfactory evidence as to the real form of 
the carbon atom has thus far been obtained. 

If the two bromine compounds are oxidized by potassium 
permanganate, two different dibrombutanediols, C 4 H 6 Br 2 (OH) 2 
are formed. These will have the structures : 



HO 



HO 




CH,Br 



HOsf 



CH 2 Br BrH 2 C 




CH 9 Br BrHptt^ 



OH 



HO 




OH 



CH 2 Br 



On studying these formulae it will be seen that the first 
compound is inactive by internal compensation, while the 



ERYTHROL. 157 

second and third are active, the one being right-handed, the 
other left-handed. By means of caustic potash the two di- 
brombutanediols are converted into the two erythrols which 
have been referred to. By oxidation the erythrol which 
melts at 12 6° is converted into mesotartaric acid, 

C0 2 H 

I 
CHOH 

I 
CHOH 

I 
C0 2 H 

the tartaric acid which is inactive by internal compensation, 
since it cannot be separated into active forms. From this 
it follows that this erythrol is also inherently inactive ; and 
it is further assumed that the erythrol melting at 72 is a 
racemic mixture of the right and left forms of an active 
compound. 

The relations which have been sketched can be repre- 
sented by means of an adaptation of ordinary formulae as 
follows : 

CH 2 H-C-CH 2 Br H H 

II II -» ' I -*+ I 

CH S H-C-CH 2 Br HO-C-CH 2 Br H-0-C-CH 2 OH 

I I I 

CH \ H-C-CH Br HO-C-CH,Br H-0-C-CH 9 0H 

II II I I 
CH 2 BrH 2 C-C-H H H 

m.p. 135 . i- Erythrol (126 °). 

\ H H 

I I 

HO-C-CH 2 Br-*H-0-C-CH 2 OH 

I I 

BrH 2 C-C-OH HOH 2 C-C-OH 

I I 

• H H 

m.p. 83 . (d+Z) Erythrol (72 ). 



158 ORGANIC CHEMISTRY. 

CH 2 OH 

I 
Hexanehexols, (CHOH) 4 . As these compounds contain 

I 
CH 2 OH 

four asymmetric carbon atoms, a very considerable number 
of isomers is possible, and several of them are known. 
The most important are mannite, which is found in manna, 
and is also formed by the reduction of glucose, fructose, or 
mannose ; dulcite, formed by the reduction of milk sugar 
and galactose ; and sorbite, formed by the reduction of 
gulose, glucose, or fructose. Since both mannite and dulcite 
give 2-iodohexane by reduction with hydriodic acid, and 
since glucose gives both mannite and sorbite by reduction, 
all three of these compounds must contain a normal chain 
of carbon atoms. The isomerism is probably due to differ- 
ences in configuration, that is, to the arrangement of the 
groups in space. This configuration has been determined 
with a good degree of certainty by methods somewhat 
similar to those which have been given for the erythrols. 

Pyrocatechol (o-dihydroxybenzene or 1.2 phendiol), C 6 H 4 

(OH) 2 , is formed by fusing o-iodophenol or o-phenolsul- 
phonic acid with caustic potash. Pyrocatechol melts at 
1 04°, and boils at 2 4o°-2 45°. It is easily soluble in water. 

Resorcinol (1.3 phendiol) is formed by melting m-iodophe- 
nol or rn-benzene-disulphonic acid with caustic potash. It 
is also formed by the fusion of o-brom phenol with caustic 
potash. This latter fact, and others like it, led at one time 
to serious confusion in the relation between the derivatives 
of benzene ; and for a number of years many compounds 
which are really ortho were called meta, and compounds 
which are really meta were called ortho. In using the 
earlier literature this must be remembered. 



RESORCINOL. 1 59 

Rearrangements of this kind appear to be especially liable 
to occur in fusions with caustic potash, and that means is 
avoided, if possible, in determining the constitution of ben- 
zene derivatives. 

Resorcinol condenses easily with phthalic anhydride to 
form fluorescein, and*it is manufactured for use in making 
this and other dyestuffs. 

When resorcinol in aqueous solution is boiled with sodium 
amalgam, while carbon dioxide is passed through the mix- 
ture, it takes up two atoms of hydrogen, but the resulting 
dihydroresorcinol does not conduct itself as a dihydroxy 
compound, but reacts sometimes as 1.3 cydohexanedione, 

PIT _(""(") 

CH 2 < 2 >CH„ and sometimes as 1.3 cydohexenoloue, 

CH 2 — CO 

CH 2 -COA CH 

CH Q < # This is a sufficiently strong acid to 

CH 2 -C-OH 

decompose carbonates, although it contains no carboxyl 
group (p. 220). 

When dihydroresorcinol is treated with sodium hypochlorite 
it gives sodium glutarate and chloroform. 



PIT CO 

CH * < CH-CO > CH2 + 3 NaC1 ° 



CH 9 C0 9 Na 



cH *<cH; C o;Na+ cHci < 

+ NaOH. 

When boiled with a solution of barium hydroxide it under- 
goes hydrolysis, giving the barium salt of y-acetylbutyric 
acid, 

CH 2 -CO /CH 9 -C O -CEL\ 

2 CH 2 / ;CH + Ba(OH),=( 1 " 8 Ba. 

CH C-OH 2 2 2 



l6o ORGANIC CHEMISTRY. 

These reactions furnish additional proof of the relation 
between the carbon atoms of cyclohexane and of benzene 
(p. ioo). Resorcinol melts at 119 , and boils at 2 7 6°. It 
dissolves in two-thirds of its weight of water at 13 . 

Hydroquinone (1-4 phendiol) is most easily prepared by the 
reduction of quinone, C 6 H 4 2 . It is readily converted into 
quinone by oxidizing agents. For this reason it is a mild 
reducing agent, and is used as such for a " developer " in 
photography. Hydroquinone melts at 169 . It dissolves in 
16 parts of water at 15 . 

Pyrogallol (1.2.3 phentriol) is prepared by the dry distilla- 
tion of gallic acid, 

C0 2 H 1 

CH< OH 3 

N OH 5 

A solution of pyrogallol in sodium or potassium hydroxide 
absorbs oxygen so rapidly that it is used for that purpose in 
gas analysis. Carbonates and acetates are formed, together 
with a small amount of carbon monoxide, and dark-colored 
decomposition products. Pyrogallol melts at 132 and boils, 
with some decomposition, at 294 . 

Phloroglucinol (1.3.5 phentriol) is interesting because, while 
its general conduct is that of a phenol, it reacts in some cases 
as though it were the 1.3.5 hexanetrione, 

rH , CO-CH 2 
CH2< CO-CH 2 >C °- 

In the foregoing discussion of alcohols the student will 
understand, of course, that only a very few, comparatively, 
have been considered. Many others might be given, some 



PHLOROGLUCINOL. l6l 

of them of at least equal importance with those which are 
mentioned. 

The following is a summary of the general methods of 
preparing alcohols : 

i. By fermentation, especially ethyl, propyl, isobutyl and 
isoamyl alcohols. 

2. By heating an alkyl halide with water, with lead oxide 
or silver oxide and water, or with potassium or silver ace- 
tate. In the last case an acetic ester of the alcohol results, 
which must be saponified. 

CH 3 I -h H 2 = CH3OH + HI. 
CH3I + C 2 H 3 2 Ag = CH 3 C 2 H 3 2 + Agl. 

Methyl acetate. 

3. By treating an unsaturated hydrocarbon with concen- 
trated sulphuric acid, diluting with water and distilling, 
which causes the saponification of the acid ester of sulphuric 
acid at first formed. 

C 2 H 4 + H 2 S0 4 = C 2 H 5 HS0 4 . 

Ethyl sulphuric acid. 

C 2 H 5 HS0 4 + H 2 = C 2 H 5 OH + H 2 S0 4 . 

If the hydrocarbon contains more than two carbon atoms, 
a secondary or tertiary alcohol will be formed, and thus a 
means is furnished of passing from a primary to a secondary 
or tertiary alcohol. (How could isopropyl alcohol be pre- 
pared in this way from normal propyl alcohol ?) 

4. By the reduction of an aldehyde, ketone, or acid 
chloride. 

C 6 H 5 C(° + 4 Na + 3 HC1 = C G H 5 CH 2 OH + 4 NaCl. 

Benzoyl chloride. Benzyl alcohol. 



1 62 ORGANIC CHEMISTRY. 

5. By treatment of an amine with nitrous acid. In the 
case of " aromatic " amines a diazo compound is formed as 
an intermediate product (p. 147). 

C 2 H 5 NH 2 + HN0 2 = C 2 H 5 OH + H 2 + N 2 . 

Ethyl amine. 

6. Fusion of an aromatic sulphonic acid or halogen com- 
pound with caustic potash, giving a phenol. 

C 6 H 5 S0 3 K + KOH = C 6 H 5 OH+ K 2 S0 3 . 

Potassium benzene sulphonate. Phenol. 

7. Oxidation of an unsaturated compound with potassium 
permanganate, giving a glycol or dihydroxy compound. 

CH 2 = CH 2 + O + H 2 = CH 2 (OH)-CH 2 (OH). 

Ethylene. Glycol. 

8. Some acids containing a tertiary hydrogen atom may 
be oxidized to a hydroxy acid by potassium permanganate. 

c R / C0 2 H / C0 2 H 

v r^rr / ^H 3 + = C 6 H 4 r(cw\\ ^ ^-"^3 • 
VL \CH 3 X ^ U±1 \CH 3 

p.-Isopropyl benzoic acid. p.-Hydroxyisopropyl benzoic acid. 

Most of the methods given can be used for the preparation 
of hydroxy acids and of hydroxyl derivatives of other com- 
pounds, as well as for the preparation of alcohols. 



Laboratory Exercises. 

1. Preparation of ethyl alcohol by fermentation. 

2. Determination of the percent of "fusel oil" in a sample 
of whisky. 

3. Preparation of allyl alcohol. 

4. Preparation of /-cresol. 



LABORATORY EXERCISES. 1 63 

5. Preparation of benzyl alcohol. 

6. Preparation of a or /3 naphthol. 

7. Preparation of glycol. 

8. Distillation of glycerol under diminished pressure. 

9. Preparation of hydroquinone. 

10. Preparation of phenyl-methyl carbinol, 

^? 5 >CHOH. 



164 



ORGANIC CHEMISTRY. 



CHAPTER XL 





ETHERS. 










Boiling Specific 






Point. 


Gravity. 


Methyl ether 


(CH 3 ) 2 


- 23.65^ 




Methyl ethyl ether 


CH 3 ^ p. 
C 2 H 5 > U 


10.8 


0.7252 (o°) 


Ethyl ether 


(C 2 H 5 ) 2 


34-6° 


0.718 (15-6°) 


Normal propyl ether 


(C 3 H 7 ) 2 


90.7 


0.7443 (21°) 


Isopropyl ether 


(cl:> ch >° 


69 


O.7247 (21°) 


Methyl propyl ether 


S?;>° 


38-9° 


0.7471 (o°) 


Isoamyl ether 


(gg*>CH-CH 2 CH 2 ) 2 


173° 
39° 


O.7807 (l S °) 


Vinyl ether 


(CH 2 = CH) 2 





Allyl ether 


(CH 2 = CH — CH 2 ) 2 


94-3° 


0.8046 (18 ) 



Methyl propargyl ether 



CH z^. C — CH.) ^^ f^. 

ch:>° 



62° 0.83 



Phenyl ether 


(C 6 H 5 ) 2 






253° 





Methyl phenyl ether (Anisol) 


CH 3 ^ n 

C fi H 5 >° 






iS5.° 


1.0110(0°) 


Ethyl phenyl ether (Phenetol) 


C 6 H 5 >° 






172° 
Above 360 

i3-5° 


0.9822 (o°) 


aa. Naphthyl ether 


(C 10 H 7 ) 2 O 




— 


Ethylene oxide 


CH 2 
CH 2 




0.8966 (o°) 


Propylene oxide 


CH 3 — CH 
CH 2 







35° 


0.859 (o°) 


■y-Pentylene oxide 


CH 3 — CH — 

1 






1 


78° 


0.8748 (o°) 




CH 2 CH 2 — 


CH 2 






Pentamethylene oxide 


CH2 <gS; = 


CH 
CH 


;>o 


82 


0.880 (o°) 



ETHYL ETHER. 165 

Ethyl ether (C 2 H 5 ) 2 0, the best known, and by far the 
most important, of the ethers, is prepared by mixing alcohol 
and concentrated sulphuric acid in such proportion that the 
mixture will distill at about 140 . A mixture of water, ether, 
and alcohol distills over, and, if alcohol is run in at such a 
rate that the boiling 4 point remains nearly constant, a given 
portion of sulphuric acid will convert a relatively large 
amount of alcohol into ether. Theoretically, an infinitely 
great amount should be so converted, but the process comes 
to an end through the formation of sulphur dioxide and other 
secondary products. 

Superficially considered, the reaction seems to consist 
merely in the removal of water from the alcohol : 

2 C 2 H 5 OH-H 2 = ^ 5 >0. 

Historical. — In the earlier study of carbon compounds the 
apparently simple relation between alcohol and ether, and 
the fact that ether has a much lower boiling point (3 4. 6°) 
than alcohol (78.3 ), led chemists to suppose that ether is a 
simpler body than alcohol, and to write the formulae C 4 H 5 
and C 4 H 5 O.HO.* Such formulae were, of course, possible 
only at a time when the determination of molecular 
weights by means of the vapor density was not considered 
reliable. 

In 1842 Gerhardt pointed out that the formula of ether 
as given above should be doubled in comparison with that 
of alcohol, basing his belief partly on the vapor densities of 
the two substances. 

It was not, however, till 185 1, when Williamson showed 
that ether is formed by heating sodium ethylate with ethyl 

* In these old formulae which were in common use by many chemists from 1830 to 
1850, and by some for a much longer period, C = 6, = 8, and water was written HO. 



1 66 ORGANIC CHEMISTRY. 

iodide, that the true relation between alcohol and ether was 
generally recognized. Williamson's reaction still remains 
the best proof of the structure of ether, and, in its generalized 
form, the best method for the preparation of many ethers. 

R - O - Na + RT = R - O - R' + Nal. 

The two radicals which are combined by this reaction may 
be identical or different. In the latter case mixed ethers, 

PTT 

as, for instance, methyl ethyl ether, *? > O, methyl phenyl 

CH W^s 

ether, or anisol, J* >0, ethyl phenyl ether, or phenetol, 

C H 6 5 

2 5 >0, and the like, are formed. Williamson's discovery 

was not only of value in establishing the structure of ether, 
but was also of far-reaching importance in its influence upon 
the views of chemists as to the atomic weights of the ele- 
ments, the formula of water, and the structure of both or- 
ganic and inorganic compounds. The discussions with 
reference to ethyl ether are, therefore, of fundamental im- 
portance in the history of chemistry. 

In considering the etherification of alcohol by means of 
sulphuric acid, it becomes evident that the reaction does not 
consist merely in the removal of water from two molecules 
of the alcohol by the acid, since both water and ether distill 
over together. When the sulphuric acid and alcohol are 
mixed, they combine, in part, to form the acid ester of 
sulphuric acid : 

C 2 H 5 OH + H 2 S0 4 = C 2 H 5 HS0 4 + H 2 0. 

Ethyl sulphuric acid. 

This acid ester then reacts,' in part, with more alcohol : 
C 2 H 5 HS0 4 + C 2 H 5 OH = (C 2 H 5 ) 2 + H 2 S0 4 . 



CHEMICAL CONDUCT. 1 67 

The water and the ether formed by the two reactions distill 
over, while the regenerated sulphuric acid remains behind. 

Physical Properties. — Pare ethyl ether is a very mobile 
liquid which boils at 34.6 , and has a specific gravity of 0.718 
at 15. 6°. It dissolves in 11.1 volumes of water at 25 , while 
it will, in turn, dissolve one-fiftieth of its volume of water. 
Because of its low boiling point, its vapors form explosive 
mixtures with air, and care is required in its use. Commer- 
cial ether usually contains alcohol, which can be removed 
by repeated washing with small amounts of water, and water, 
which can be mostly removed by calcium chloride and the 
last portions by means of sodium, best in the form of wire. 
On account of its volatility, ether should be kept in tightly- 
corked, strong bottles, and these are best filled full. 

Chemical Conduct. — In their chemical conduct the ethers 
are generally very stable bodies, and remain unchanged 
when boiled with solutions of alkaline hydroxides or dilute 
acids. Concentrated sulphuric acid gives with ethyl ether, 
however, ethyl sulphuric acid, and hydriodic acid gives 
alcohol and ethyl iodide : 

(C 2 H 5 ) 2 + 2 H 2 S0 4 = 2 C 2 H 5 HS0 4 + H 2 0. 
(C 2 H 5 ) 2 + HI = C 2 H 5 OH + C 2 H 5 I. 

In some cases of mixed ethers containing one strongly nega- 
tive group the ethers may be decomposed by boiling with 
caustic potash. Thus the ethyl nitrodimethylphenyl ether 
may be decomposed in this manner : 

/CH 3 1. /CH 3 

pu / CH 3 3. yrr\TT _ r rr / CH 3 + C 2 H 5 OH. 

^6^2 N oC 2 H 5 4. + KUM ~ ^^ \ OK 
\N0 2 5. \N0 2 



1 68 ORGANIC CHEMISTRY. 

One of the alcohols or phenols in such cases is decidedly 
acid in character, and the decomposition resembles the 
saponification of esters (p. 283). It is worthy of notice that, 
with an increase in negative properties, the stability toward 
water and alkalies for groups united with oxygen decreases. 
Thus ethyl ether cannot be decomposed by water or alkalies, 

acetic ester, CH 3 C — O— C 2 H 5 , is readily decomposed by 
alkalies and slowly by water, and acetic anhydride, 

O O 

// % 

CH 3 - C - O - C- CH 3 

is quite readily decomposed by water. A somewhat similar 
instability in the union of carbon atoms, occasioned by the 
presence of negative groups, will find mention later (p.351). 

It need scarcely be said that very many ethers are known, 
but none of the simple ethers require further mention here. 
No simple ethers of tertiary alcohols are known, but several 
mixed ethers derived from such alcohols have been prepared. 

CH 2 

Ethylene Oxide, | > O, may be considered as a cy- 
CH 2 

clic ether. It is prepared by treating glycol c/ilorkydrm, 

CH 2 OH 

(i-chlorethanol-2), I , with caustic potash, or by treat- 

CH 2 C1 

CH 2 -0-C 2 H 3 

ing glycol monoacctate, | , with hydrochloric 

* CH 2 OH 
acid gas, and the resulting product with caustic potash. 
Ethylene oxide boils at 13.5 , and has a specific gravity of 
0.8966 at o°. It mixes with water in all proportions. 



ETHYLENE OXIDE. 1 69 

Ethylene oxide combines directly with acids forming esters 
of glycol : 

CH 2 CH 2 C1 

I >0 + HCl= I 

CH 2 CH 2 OH 

CH 2 CH 2 -0-C 2 H 3 

I >0 + C 2 H 4 2 = I 

CH 2 CH 2 OH. 

These reactions bring out the very marked difference 
between ethylene oxide and the ordinary ethers. 

Laboratory Exercises. 

1. Preparation of ethyl ether. 

2. Preparation of anisol. 



170 ORGANIC CHEMISTRY, 



CHAPTER XII. 
ALDEHYDES AND KETONES. 

Boiling Specific 

Point. Gravity. 

Formaldehyde (Methanal) HCHO — 21° 0.8153 (— 20 ) 

Acetaldehyde (Ethanal; CH 3 CHO 20. 8° 0.8009 (°°> 

Propionic aldehyde (Propanal) CH s CH 2 CHO 48.8 0.8320 (o°) 

Butyric aldehyde (Butanal) CH 3 CH 2 CH 2 CHO 74° 0.911(0°) 

Isobutyric aldehyde (Methyl propanal) 

£U»>CH — CHO 6l ° 0.8618(0°) 

Valeric aldehyde (Butanal) CH 3 CH 2 CH 2 CH 2 CHO 103.4" 0.8185(11.2°) 

Isovaleric aldehyde (2-Methyl butanal-4) 

^[j 3 >CHCH 2 CHO 92° 0.8222(0°) 

Caproic aldehyde (Hexanal) CH 3 (CH 2 ) 4 CHO 129° 0.8498(0°) 

Oenanthaldehyde (Heptanal) CH 3 (CH 2 ) 5 CHO 155° 0.8231 (15°) 



Acrolein (Propenal) CH 2 = CH — CHO 52.4° 

Crotonic aldehyde (2-Butenal) CH 3 CH = CHCHO 104° 1,033 (°°) (?) 

Tiglic aldehyde (2-Methyi-2-butenal) 

CH 3 CH = C < gg-5 117° 0.871 (15°) 



Tetramethylene aldehyde (Methylalcyclopentane) 



CH 2 <£gf>CHCHO Il6C 



A 1 Cyclopentene aldehyde (Methylalcyclopentene-i) 
CH 2 — CH 2v 
I X C-CI 

CH, — CH O 



Benzaldehyde (Phenmethylal) C 6 H 5 CHO 179-5° 1.0636(0°) 

Phenyl acetaldehyde (Phenethylal) C fi H 5 CH 2 CHO 193 1.085 

o-Toluic aldehyde (Methylphenmethylal-2) 

C 6 H 4 <gg b J 200 ° 

Hydrocinnamic aldehyde (Phenpropylal) 

3 C H 6 CH 2 CH 2 CHO 208° 



ALDEHYDES AND KETONES. 171 



Cuminic aldehyde (4-metho-ethylphenmethylal) 



C 6 H 4 <^ ^CH 3 237° 0.9832(0°) 

CHO 4 



Cinnamic aldehyde (phenpropenylal) 

C 6 H 5 CH = CHCHO 129 (20 mm) 1.0497 (24 ) 



a-Naphthaldehyde (naphthenemethylal) C 10 H 7 CHO 291 .6° 



Acetone (propanone) CH 3 COCH, 56.5° 0.818 (o°) 

Methyl ethyl ketone (butanone) CH ;i COC 2 H r> 80.6 0.8296 (o°) 

Diethyl ketone (3-pentanone) CH'!cH 2 ^ >CO i02 ° 0.8264(0°) 

Methyl propyl ketone (2-pentanone) 

CH,CHoCH 9 \ r^r\ n o / i> 

3 "CH"'- >CO io2 -7 0.8335(0°) 

Methyl isopropyl ketone (methyl butanone) 

CH,'> CH >CO 95° 0.822(0°) 

CH, 
Pinacolin (dimethyl butanone) 



(CH,) 3 = C 



CH > CO Io6 ° °- 8z6 5 ( ° 0) 



Ethylidene acetone (2-pentenone) 

CH 3 CH = CH ^ CQ i220 q g6i (i . 0) 

3 /CH 2 

2-Methyl-i-butenone-3 CH,— CO — C / „„ ioo° 

\ Cri, 

Mesityl oxide (2-methyl-2-pentenone-4) 



CH, 
CH, 



> C = CH — CO — CH, 130 0.8706 (4°) 



Acetyl trimethylene (ethanoyl cyclopropane) 

CH 2 

CH,COCH< I 115° 

CH 2 

CH 2 — CH 2 

Adipic ketone (cyclopentanone) | ^> CO 130° 0.9416(21.5°) 

CH 2 — CH 2 

CH 2 — CH 2 CO 

Pimelic ketone (cyclohexanone) I S4-5° °-9473 ( 2 °°) 

CH 2 — CH 2 CH 2 
CH 2 — CH 2 — CH 2 
Suberone (cycloheptanone) | ^> CO 178. 5 0.9685 (o D ) 

CH 2 — CH 2 — CH 2 

CH, — CH — CO 



CH 2 it 



2,33 Trimethyl cyclopentanone CH 2 168° 0.8956 (20°) 

gfcxl— <k 

/-Menthone (2-methyl-5 -propyl cyclohexanone) 

CH 3 — CH<gg~gg2- >CH _ CH< CH 3 2070 0.896(20°) 



72 



ORGANIC CHEMISTRY, 



CH 2 — CO 
i-Methyl cyclopentene-i-one-5 CH 2 <^ iS7 c 

CH = C — CH, 
Catnphorphorone 



CH 3 — CH — CO 
CH 2 — CH 2 



>c = c< 



CH 3 
CH. 



203 1 - 



CH, 



Camphor 



CH 3 

C CO 

CH3 — C — CH 3 
CH 2 CH CH 2 



Geranial, Citral (2,6-dimethyl-2,6-octadienal-8) 
/-.tt' ^> C = CH — CH 2 — CH 2 — Cs\ pjj 3 _ 



CHO 



226° 



0.9808 (16 ) 



0.939 (12 ) 



0.897 (isl 



Acetophenone (ethylonephen) C 6 H f) COCH 3 202 1.032 (15 ) 

Ethyl phenyl ketone (i^propylonephen) C 6 H 5 COC 2 H 5 215. 5 1.009 (o°) 
Methyl benzyl ketone (i 2 -propylonephen) 

C c H 5 CH 2 COCH 3 215° 1.010(3°) 



CH 3 CH 3 
\/ 
Irone CH C CH— CH = CHCOCH 3 

II I 

CH— CH,- CH— CH, 

CH 3 CH 3 

\V 

Ionone CH 2 — C CH — CH = CHCOCH, 

I I 

CH=CH-CH-CH, 



144° (16 mm) 0.939 (20 ) 



C27 (12 mm) 0.935 (20 "•) 



Diacetyl (butanedione) CH 2 COCOCH 3 88° 0.9734 (22 ) 

Acetylacetone (2,4-pentanedione) CH 2 COCH 2 COCH 3 137 0.987 (15 ) 
Acetonylacetone (2 ,5-hexanedione) 

CH 3 COCH 2 CH 2 COCH 3 194 0.969 (20 ) 



Dihydroresorcinol (1,3-cyclohexanedione) "1 

cH 2 <cg;=88> cH 2 | 

or (cyclohexene i-ol-2-one-6) 

CH 2 — C0\ pu 

OH 



CH 2 < 



CH, 



Melting Point. 



Benzoquinone (cyclohexadiene 1,4-dione 3,6) 

CH = 
CH = 

Benzil (diphenylethanedione) C 6 H n COCOC 6 H 



co <ch = ch> co 



95° 



ALDEHYDES. 1 73 

O 



t, 4 Naphthoquinone 



t, 2 Naphthoquinone 



O 
O 

o 



Anthraquinone 

Phenanthrenquinone 205 

O \ / 



CCO 

Aldehydes I \\ ) and Ketones f \\ ) have 

VR - C - H/ VR - C - R/ 

already been referred to as the first oxidation products of 
primary and secondary alcohols respectively. This method 
of preparation for them is the simplest and most common. 
The oxidizing agent usually employed is chromic acid, or a 
mixture of potassium or sodium pyrochromate and sulphuric 
acid. Alkaline oxidizing agents can rarely be used, as alde- 
hydes, especially, are sensitive toward alkalies. 

Nomenclature. — Aldehydes are named, officially, by adding 
"-al," and ketones, by adding "-one " to the name of the 
hydrocarbon from which they are derived. The older names 
for the aldehydes, which are still more generally used, are 
derived from the name of the acid which results from their 
further oxidation. Thus the aldehyde frOm ethyl alcohol is 
called acetaldehyde because by further oxidation it gives 
acetic acid. Ketones are very often named by means of the 
groups connected by the carbonyl group ; thus pentanone-2 , 
CH 3 COCH 2 CH 2 CH 3 , is called methyl propyl ketone. 

Formaldehyde (methanal), CH 2 0, is formed by passing 
a current of air through methyl alcohol heated to 40 — 
50 , and conducting the resulting mixture of vapors over 



174 ORGANIC CHEMISTRY. 

a heated copper spiral. It is also formed by the incorrb 
plete combustion of vapors of methyl alcohol in contact with 
platinum gauze or platinized asbestos. For disinfecting pur- 
poses, specially constructed lamps, based on this principle, 
have been devised. 

Formaldehyde is a gas at ordinary temperatures, but may 
be condensed to a liquid which boils at -21 . In pure con- 
dition it readily passes over into a polymeric form called 
oxy methylene or metaform aldehyde, (CH 2 0) x . In dilute solu- 
tions, however, it exists in the simple form CK 2 0, or perhaps, 
in part, as CH 2 (OH) 2 . 

Formaldehyde combines directly with ammonia in aqueous 
solutions, to form hexamethylene amine. 

6 CH 2 -h 4 NH 3 = (CH 2 ) 6 N 4 + 6 H 2 0. 

The name is unfortunate, as it is liable to confusion with 
the common name for an amine derived from cyclohexane. 

Under the action of lime-water formaldehyde condenses to 
form a sugar, a-acrose (C 6 H 12 6 ) (p. 363). From the ease with 
which formaldehyde undergoes condensation, and from the 
fact that it may be considered as a reduction product of car- 
bonic acid, it has been suggested that formaldehyde may be 
the first step in the formation of starch and other carbohy- 
drates in the leaves of plants. (Baeyer, Ber. chem. Ges. 3, 67 ; 
Wurtz, Ibid. 5, 534; Reinke, Ibid. 14, 2148; Loew, Ibid. 
22, 482 \J.prakt. Chem. [2] 33, 344.) 

Formaldehyde, both as a gas and in solution, is a powerful 
germicide, and is extensively used as a disinfectant and food 
preservative. The commercial aqueous solution is known as 
formaline. 

In a dilute alkaline solution, hydrogen peroxide oxidizes 
formaldehyde quantitively to a formate. 

CH 2 + NaOH + H 2 2 = NaHCQ 2 + 2 H 2 0. 



STRUCTURE OF ACET ALDEHYDE. 1 75 

Acetaldehyde (ethanal), CH 3 — C^ TT , is prepared by oxi- 

dizing ethyl alcohol with sodium or potassium pyrochromate 
and sulphuric acid. 

3 C 2 H e O + Na 2 Cr 2 0,+ 4 H 2 S0 4 = 

3 C 2 H 4 + 2 NaCr(S0 4 ) 2 + 7 H 2 0. 

It may also be prepared by heating a mixture of calcium 
acetate and formate : 

(CH3CO . 0) 2 Ca + (H . C0 2 ) 2 Ca = 2 CH 3 - H f ° + 2 CaC0 3 . 

Ordinary alcohol undergoes partial oxidation in contact 
with heated platinum and air, forming acetaldehyde in the 
same manner that formaldehyde is formed from methyl 
alcohol. 

Acetaldehyde is a colorless liquid with a very penetrating, 
characteristic odor. It boils at 21 , and has a specific 
gravity of 0.795 at io°. 

Structure of Acetaldehyde. — The view held of- the structure 
of acetaldehyde depends, in the first place, on the ease with 
which it is oxidized to acetic acid. 

C 2 H 4 + O = C 2 H 4 2 . 

Since sodium acetate gives methane when heated with 
sodium hydroxide, it must contain all of its hydrogen atoms 
combined with one of the carbon atoms, that is, it contains 
a methyl group, and the reaction may be written, 

CH 3 C0 2 Na -f NaOH = CH 4 + C0 3 Na 2 . 

It follows from this that acetaldehyde also contains a 
methyl group and has the structure, CH 3 . CHO. 



176 ORGANIC CHEMISTRY. 

It still remains to determine the structure of the group 
CHO, which is characteristic of all aldehydes. The struc- 
ture of this group is established by the action of phosphorus 
pentachloride upon it. 

CH3CHO + PC1 5 = CHgCHCL, + COCl 3 . 

Ethylidene chloride. 

It appears from this reaction that two chlorine atoms may 
take the place of the oxygen atom, and from this we seem to 
be justified in the conclusion that this oxygen atom is doubly 
united with carbon. The full structure is, therefore, 

H H 

I I 
H-C-C=0 
I 
H 

The double union between carbon and oxygen may be 
looked upon in somewhat the same light as a double union 
between carbon atoms (p. 79). Oxygen in this condition 
occupies a greater atomic volume than when singly united 
with carbon or other atoms (p. 41), and the aldehyde (or 
ketone) group reacts very easily with a great variety of 
substances. In other words, a double union is weaker than 
a single one. 

Polymeric Forms. — The addition of a small amount of 
hydrochloric or sulphuric acid causes acetaldehyde to change 
to a polymeric form, paraldehyde (C 2 H 4 0) 3 which boils at 
1 2 5 and has a specific gravity of 0.99925 at 15 . At o° 
a very little gaseous hydrochloric acid will convert acetal- 
dehyde partly into metaldehyde, (C 2 H 4 0) 3 , a solid compound 
which sublimes without melting at 112 — 115°. The poly- 
merization is, in both cases, accompanied by an evolution 



CONDENSATION OF ALDEHYDE, 1 77 

of heat. Since both paraldehyde and metaldehyde can 
be converted back into ordinary aldehyde by heat, or by 
distilling with a little sulphuric acid, it seems probable that 
the molecule is held together by means of oxygen atoms 
rather than by carbon, and the structure is most likely, 

H H 

I I 

C C 

/ I \ / I \ 

H O CH 3 OH HO CH 3 O CH 3 

I / \ I I / \ I 
C O C C o c 

I I ■ I I 

CH 3 CH 3 CH 3 H 

By this method of writing the formulae it is intended to 
indicate that in one polymer the three methyl groups are on 
the same side of the plane of the ring of carbon and oxygen 
atoms, while in the other two methyl groups are on one side of 
the plane of the ring, and one on the other. Which formula 
represents the structure of paraldehyde and which the struc- 
ture of metaldehyde is, at present, merely a matter of con- 
jecture. 

Condensation of Aldehyde. — Under the influence of zinc 
chloride, or of an aqueous solution of potassium carbonate, 
acetaldehyde condenses to aldol, C 4 H 8 2 . In this case the 
condensation has taken place between the carbon atom of 
the aldehyde group and that of a methyl group in the sec- 
ond molecule of the aldehyde. This is proved by the follow- 
ing relations Aldol, when distilled, gives crotonaldehyde, 
C 4 H 6 ; this, by oxidation, gives crotonic acid, C 4 H 6 2 , and 
this, by reduction, normal butyric acid, which has the struc- 
ture CH 3 CH 2 CH 2 C0 2 H. These relations can be most 



I78 ORGANIC CHEMISTRY. 

satisfactorily explained by the structural formulae which 
follow : 

rH _p^° znci 2 /OH ^0_h 2 o //£> 

3 \H -^CH 3 -CH-CH 2 -C-H-»CH 8 CH=CH-CH. 

Aldol (Butanalol — 3). Crotonic aldehyde. 

% CH 3 CH = CH — C0 2 H % CH 3 CH 2 CH 2 C0 2 H. 

Crotonic acid. Butyric acid. 

It should be noticed that in this, and in other condensa- 
tions, * one molecule divides itself into two parts (here H and 

-CH 2 — C / J which add themselves respectively to the oxy- 
gen and carbon of the aldehyde groups. Such condensa- 
tions are not only useful in many organic syntheses, but 
doubtless, also, play an important part in the life processes 
of plants and animals. 

Derivatives of Acetaldehyde. — Acetaldehyde combines 
directly with hydrocyanic acid to form a compound called 
the cyanhydrin of acetaldehyde. In this the carbon of the 
hydrocyanic acid is combined directly with the carbon of 
the aldehyde group, since hydrochloric acid and water con- 
vert it into lactic acid, and lactic acid, in turn, can be re- 
duced to propionic acid by means of hydriodic acid. 

^O hcn /OH 

CH 3 -C-H -> CH 3 -C-CN 

X H 

Acetaldehyde cyanhydrin. 
HCl + HoO /OH HI 

-> " CH 8 -CH-C0 2 H->CH 3 CH 2 C0 2 H. 

Lactic acid. Propionic acid. 

* Some authors use the term " condensation " exclusively of reactions in which car- 
bon unites with carbon. Such a narrowing in the use of the term does not seem desir- 
able. It is used here and elsewhere to express the combination of two molecules into 
one, with or without the simultaneous or subsequent elimination of water, hydrochloric 
acid or some other simple compounds. 



DERIVATIVES OF ACET ALDEHYDE. 179 

The reactions here given are very generally useful for the 

preparation of a-hydroxy * acids from aldehydes and ketones. 

Acetaldehyde combines directly with ammonia, to form a 

well crystallized compound, aldehyde ammonia, which prob- 

/OH 
ably has the structure, CH 3 -C-NE„ Dilute acids readily 

\H 
regenerate aldehyde from this compound, and it may be 
used in the preparation of pure aldehyde. 

Acetaldehyde combines with acid sodium sulphite to 
form a double compound which, from analogy, is probably, 

/OH 
CH 3 — C— S0 3 Na. As similar double compounds with other 

\H 
aldehydes and ketones often crystallize well, they are used, 
in many cases, for the purpose of purifying these bodies. 

Acetaldehyde reacts with hydroxylamine to form an oxime, 
with phenylhydrazine to form a hydrozone and with semi- 
carbazine to form a semicarbazone. 

//O /H 

CH 3 - H - H + NH 2 OH = CH 3 -C = N-OH + H 2 0- 

Acetaldoxime. 

CH 3 - C - H + C,H S NHNH ( 

Phenylhydrazine. / U 

= CH 3 -C = N-NHC 6 H 5 + H 2 0. 



Hydrazone of acetaldehyde. 



CM3_ \H+ \NH 2 



Semicarbazine. 

= CH 3 -C = N-NH-CO-NH 2 + H 2 0. 

Semicarbazone of acetaldehyde. 

* Groups which are combined with the carbon atom which is adjacent to the car- 
boxyl group are said to be in the a-position ; groups combined with the second carbon 
atom are in the ^-position ; with the third, y ; with the fourth, S ; with the fifth, e ; with 
an end carbon atom w. 



180 ORGANIC CHEMISTRY. 

The oximes, hydrazones, and semicarbazones of aldehydes 
and ketones are very often used for purposes of identifica- 
tion, as they are usually crystalline and easily purified. 

Oxidation and Reduction. — Acetaldehyde may be reduced 
to ethyl alcohol, and it may be readily oxidized to acetic 
acid. It is, therefore, intermediate between these two sub- 
stances, 

//O //C) 

CH 3 CH 2 OH -£ CH 3 - G — H ->- CH 3 - C - OH. 

Many other aldehydes of the marsh-gas series are known, 
but their general methods of preparation and chemical prop- 
erties resemble those of acetaldehyde so closely as to require 
no special mention. 

^o 

Acrolein (propenal) , CH 2 = CH — C — H, is the first 
aldehyde of the ethylene series. An aldehyde of this series 
containing but two carbon atoms would have the structure, 

CH — C — H. The study of carbon compounds containing 
a bivalent carbon atom seems to indicate that such com- 
pounds can have an independent existence only when the 
atom or group combined with the carbon atom is strongly 
negative, as in the compounds CO, C = NH and a few 
others. When the group is less negative, as in the case under 
consideration, the bivalent carbon atom has so great an 
affinity for other atoms or groups as to cause the immediate 
polymerization of the compound. 

Acrolein is prepared from glycerol by distilling it with 
acid potassium sulphate. It is also formed in small amount 
by the destructive distillation of fats, and is one cause of the 
disagreeable odor caused by heating oils and fats to a high 
temperature. The formation results from the abstraction of 



GERANIAL OR CITRAL. iSl 

water from glycerol. This would naturally give an unsatur- 
ated alcohol, 

CH 2 OH,CHOH,CH 2 OH- 2 H 2 = CH 2 =C = CHOH, 

but, if such an alcohol is formed at all, it immediately 
rearranges itself to form the aldehyde (p. 180). Acrolein is 
a liquid which boils at 52.4 . It has a penetrating, irri- 
tating odor, and affects the eyes strongly. Acrolein may be 
reduced to allyl alcohol, and may be oxidized to acrylic acid, 

CH 2 =CH-C-0-H. The presence of the double union, 
which is easily attacked by the oxidizing agent, makes the 
oxidation difficult, and it is practically better to prepare 

dibromacrolein, CH 2 BrCHBrCH, and oxidize this to di- 
dibrompropionic acid, CH 2 BrCHBrC0 2 H. The latter yields 
acrylic acid by reduction. This case furnishes an excellent 
illustration of the manner in which indirect, and apparently 
roundabout methods are often used to advantage in the 
preparation of organic compounds. 

Acrolein does not combine with acid sodium sulphite. 

Crotonic Aldehyde (2-butenal), CH 3 — CH=CH-CHO, has 

been incidentally mentioned in connection with aldol (p. 177). 

Geranial or Citral (2,6-dimethyl-2,6-octadienal), 

CH x CH3 

*>C=CH-CH 2 -CH 3 -C = CH-CHO, is found in 

CJHL3 

oil of lemons and of citrons, and is prepared by the oxidation 
of the corresponding alcohol, geraniol. Geraniol is found in 
geranium oil and oil of roses. Geranial when heated to 170 
with KHS0 4 condenses to cymene. The condensation is 
similar to the formation of aldol (p. 177), but with the differ- 
ence that the condensation takes place within the same mole- 



1 82 ORGANIC CHEMISTRY. 

cule. It is to be noticed that the ring which results contains 
six carbon atoms and that similar condensations often occur 
in which the resulting ring contains five or six atoms. 

Geranial is of especial interest, also, because of its use in 
the preparation of ionone, the artificial oil of violets. 

Benzaldehyde (Oil of Bitter Almonds), C 6 H 5 — c' . 

Amygdalin, a glucoside which is found in bitter almonds, 
peach stones, and several other vegetable substances, under- 
goes fermentation under the influence of emulsin, a soluble 
ferment usually associated with amygdalin, and is decom- 
posed into benzaldehyde, glucose, and hydrocyanic acid. 

C 20 H 27 NO n + 2 H s O = C 6 H 5 CHO + HCN + 2 C 6 H 12 6 . 

Amygdalin. Glucose. 

Benzaldehyde is prepared commercially by heating ben- 
zalchloride, from toluene, with milk of lime. 

C 6 H 5 CHC1 2 + Ca(OH) 2 = C 6 H 5 CHO + CaCl 2 + H 2 0. 

It may also be prepared by oxidizing benzyl chloride, 
C 6 HrCH 2 Cl, with nitrate of lead or barium, or by the 

/yO _ 
reduction of benzoyl chloride, C 6 H 5 C — CI 

Benzaldehyde is an oil which solidifies at — 13. 5 and 
boils at 179°. Its specific gravity— 1.0504 at 15 . It has a 
pleasant odor, and is used for flavoring and in perfumes. It 
is used also in the manufacture of colors of the malachite 
green group, and is extensively employed in the synthesis 
of organic compounds. 

Benzaldehyde oxidizes readily to benzoic acid, if exposed 
to the air, but the rate of oxidation is much lessened by the 
presence of a little hydrocyanic acid. 



STEREOISOMERISM OF NITROGEN COMPOUNDS. 1 83 

Chlorine converts benzaldehyde into benzoyl chloride, 
C-HrC v „. , a reaction which is rather unusual for alde- 

6 5 N Q > 

hydes, but one which is of great interest because of its use 
by Wohler and Liebig in their classical study of the radical 
benzoyl, C 6 H 5 CO (Asm. Chem. (Liebig), 3, 262). 



N — OH, is of especial interest, 
because it exists in two forms which are supposed to be 
stereoisomers. The a-benzaldoxime, or anti-benzaldoxime, is 
formed by the action of hydroxyl amine on benzaldehyde. 
It melts at 35 . The /3-benzaldoxime or syn-benzaldvxime is 
formed by the action of hydrochloric acid on a solution of 
the a-oxine in ether. It melts at i2 8°-i3o°. 



Stereoisomerism of Nitrogen Compounds. — To explain the 
isomerism of these and of a number of other oximes 
Hantzsch and Werner {Ber. chem Ges. 23, 2764 (1890)) have 
proposed a hypothesis which is stated as follows : 

" The three valences of the nitrogen atom are, in certain 
compounds, directed toward the corners of a tetrahedron 

(which is, in any case, not a regular one), ^ 

whose fourth corner is occupied by the / \ 

nitrogen atom itself." ( 1 

This idea is most clearly represented, \r°/~ ~^^y 
graphically, by picturing the center of grav- V^ZZ^^ 
ity of the nitrogen atom as occupying the Fig. 28. 

center of a sphere, while the three valences occupy positions, 
not on the equator, but on a parallel of the sphere, at a, b, c, 
of the figure. 

In accordance with this view the two oximes may be rep- 
resented by the figures : 



1 84 



ORGANIC CHEMISTRY. 



C e H 





HO 



a-(Anti)benzaldoxime. /3-(Syn)benzaldoxime. 

Fig. 29. 

The chief experimental basis for the theory lies in the 
fact that the /3-oxime when treated with phosphorus tri- 
chloride gives benzonitrile, C C H 5 -C= N, while the a-oxime 
gives, in part, with the same reagent, a chloride, 

C 6 H 5 -CH = NCI, 

and further that the acetyl derivative, 

C 6 H 5 -CH = N-0-C 2 H 3 0, 

of the (3 compound gives benzonitrile, C 6 H 5 C = N, quantita- 
tively on warming gently with a solution of sodium carbonate, 
while the a compound is saponified with regeneration of the 
oxime by the same reagent. From these facts the conclusion 
is drawn that the hydrogen atom and hydroxyl group are 
nearer together in the (3 than in the a-oxime. The prefixes 
" syn " (together) and " anti " (opposite) are given to indicate 
this relation. 

The hypothesis is an interesting and ingenious one, and 
is often referred to in the literature. It is, perhaps, the best 
explanation of these and similar compounds at present avail- 
able, but it must be admitted that it rests on a far less satis- 
factory basis than the similar hypothesis with regard to the 
stereoisomerism of carbon compounds. 

Condensation of Benzaldehyde. — When a solution of benzal- 
dehyde, in dilute alcohol containing a little potassium cy- 



SALICYLIC ALDEHYDE. 1 85 

anide, is boiled for a short time, the aldehyde condenses to 
benzoin, C 6 H 5 CHOHCOC 6 H 5 , a compound which is part 
alcohol and part ketone. This is easily oxidized to benzil, 
C 6 H 5 — CO — CO — C 6 H 5 , a 1.2 di-ketone, or, as it is often 
called, an orthodiketon, which is of especial interest because 
it forms three isomeric dioximes. In the terms of the theory 
just given these are written : 



C 6 H 5 — C — C — C 6 H 5 C 6 H 5 — C — C — C 6 H 5 

II II II II 

HO-NHON HO-N N-OH 

a-(Amphi)-benzil dioxime, m.p. 237 . /3-(Anti)-benzil dioxime, m.p. 206 . 

C 6 H 5 — C — C — C 6 H 5 

II II 

N-OH H-O-N 

■y-(Syn)-benzil dioxime, m.p. i64°-i66°. 

The configuration assigned to the y-dioxime is based on 

C 6 H 5 -C = N-OC 2 H 3 
the fact that its diacetyl derivative, | , 

C 6 H 5 -C = N-OC 2 H 3 
yields, on saponification, an anhydride, diphenylfwazane, 

C 6 H 5 C = N ^ 

I O. The configurations of the a- and /?-diox- 

C 6 H 5 C = N " 

imes are based on their conduct with phosphorus pentachlo- 
ride. Some transformations of the compounds are not, 
however, consistent with the configurations which are 
given. 



Salicylic Aldehyde (o-hydroxybenzaldehyde). C 6 H 4 < 

Oxi 2 

When a mixture of phenol and chloroform is warmed with a 

solution of caustic potash, both o- and ^-hydroxybenzaldehyde 



1 86 ORGANIC CHEMISTRY. 

are formed. The former is easily volatile with water vapor, 
and can be separated by that means. 

C 6 H 5 OH + CHCl 3 +4KOH = C 6 H 4 <^ + 3 KCH-3H 2 0. 

Salicylic aldehyde boils at 19 6°, and has a specific gravity 
of 1. 1 72 at 15 °. It can be easily reduced to the correspond- 
ing alcohol, saligenin, C 6 H 4 < 2 , or oxidized to the 

corresponding acid, salicylic acid. 

The reaction given for the preparation of salicylic alde- 
hyde is known as the Reimer-Tiemann reaction (Ber. d. chem. 
Ges. 9, 423, 824 ; 10, 63, 213), and has been useful in many 
syntheses. The aldehyde group always enters in either the 
ortho or the para position with regard to the hydroxyl group. 
/CHO 1 

Vanillin, C 6 H 3 — OCH 3 3, the active principle of vanilla, has 
\OH 4 
been prepared by this means from guaiacol, or the mono- 

methylether of o-dihydroxybenzene, C 6 H 4 < 3 . Va- 

(JJH. 2 

nillin crystallizes in needles which melt at 8i°. Since the 

aldehyde group, from what has been said, must be in either 

the ortho or para position with regard to the hydroxyl group, 

/C0 2 H 1 
and since vanillin gives firotocatechnic acid, C 6 H 3 — OH 3, 

\OH 4 
by fusion with caustic potash, the structure given above is 
established. (In this and similar cases the student should 
study the relations till he sees the force of the proof given.) 
Commercially vanillin is prepared from engenol, 

/CH 2 -CH = CH 2 1 

C 6 H 3 — OCH 3 3, 

\OH 4 



ACETONE. 187 

an oil found in a number of different plants. (Ber. d. chem. 
Ges. 9, 273.) 

/CHO 
Piperonal, C 6 H 3 — q. r u has been prepared by heating 

protocatechuic aldehyde with methylene iodide and caustic 
potash, 

/CHO 
QH3-OH -f 2 KOH + CH 2 I 2 

\OH 

/CHO 

= C 6 H 3 ~q>CH 2 + 2 KI + 2 H 2 0. 

Piperonal is prepared commercially by the oxidation of 
piperic acid with a neutral solution of potassium permangan- 
ate. If proper precautions are taken, racemic acid (p. zzi) 
is formed at the same time. 



O 
\0 

Piperic acid. 



CH 2 ^ X>C 6 H 3- CH=:CH - CH = CH-C0 2 H+40+H,0 



n CHOH-C0 2 H 

= CH 2 / >C 6 H 3 CHO+ I 

u CHOH-C0 2 H 

Racemic acid. 

Piperonal melts at 37 and boils at 263 . It has an odor 
resembling heliotrope, and is used in perfumery. 

Ketones, R— CO— R. 

Acetone, or dimethylketone (propanone), CH 3 COCH 3 , is 
the simplest of the ketones. It is prepared by the distilla- 
tion of calcium acetate : — 

ch!- ^coo >Ca = ch' >co + CaC ° 3 * 



1 88 ORGANIC CHEMISTRY. 

It is also formed by heating 2-brompropylene with mercu- 
ric oxide and acetic acid. 

2 CH 3 -CBr = CH 2 + HgO + H 2 

= HgBr 2 + CH 3 -C(OH) = CH 2 = CH 3 -CO-CH 3 . 

The reaction would lead us to expect the formation of an 
unsaturated alcohol, but this, if formed, rearranges itself to 
the ketone structure (pp. 139, 141). It is worthy of note, 
however, that, with metallic sodium, acetone gives an un- 
stable compound which, from its conduct, has the structure 

S) c -°- Na - 

(Freer, Am. Ch.J., 12, 355.) 

Acetone is a mobile liquid which boils at 56.5 . Phos- 
phorus pentachloride converts it into 2.2 dichlorpropane and 
2-chlorpropylene. Chromic acid oxidizes it to acetic and 
formic or carbonic acids. Hypochlorites convert it into 
chloroform and an acetate (p. 199). These facts, together 
with its formation from calcium acetate, furnish the basis for 
the view held of its structure. 

By reduction acetone gives isopropyl alcohol. There is 
formed at the same time a glycol called pinacone, 

OH OH 

CH 3 >C _C < CH3 - 
CH 3 CH 3 

Its formation can be explained by supposing that, as one 

hydrogen atom adds itself to the oxygen of the acetone, the 

CH 3 „ / OH, 
group, >C. which results, combines with another 

CH 3 \ 

of the same sort to form the pinacone. Similar pinacones 

are often formed by the reduction of ketones, and, in some 

cases, from aldehydes. 



DERIVATIVES OF ACETONE. 1 89 

When boiled with dilute acids pinacone undergoes a re- 
arrangement, with loss of water, forming a pinacoline. 

^ 3 >C(OH)C(OH)(^ 3 -H 2 = CH 3 -CO-C-CH 3 . 
CH 3 • \CH 3 \CH 3 

Dimethylbutanone. 

In this case, one methyl group must pass from combina- 
tion with one carbon atom to combination with the one 
adjacent. While rearrangements like this do not often 
occur, they are sufficiently frequent to furnish a warning 
against hasty conclusions with regard to the structure of a 
given compound, when based on only a few relations to 
other substances. 

Derivatives of Acetone. — Acetone combines with acid 

sodium sulphite to form a double compound, C 3 H 6 O.HNaS0 3 ; 

CTT / OT-T 

with hydrocyanic acid to form a cyanhydrin 3 >C X 1 

Cri 3 ^ CJN 

which gives, with hydrochloric acid, hydroxyisobutyric acid, 

CHo / OH . . 

> L ; with nydroxylamme to form acctoxi?7ie, 

Lrl 3 x C(J 2 ri 

pxr 

3 >C = NOH; with phenyl hydrazine to form a phenyl ' hy- 
LH 3 

PTT 

drazone, 3 > C = N — NHC 6 H 5 ; and with semicarbazine, 
CH 3 

co /NH * 

\NH- NH 2 , 

pTT 

to form a semicarbazone, _ TT 3 > C= N — NH — CO — NH 2 . 

CH 3 

In the formation of these compounds the analogy between 
ketones and aldehydes is so close that no further considera- 
tion of them is required. 

Acetone condenses with benzaldehyde, in presence of 



190 ORGANIC CHEMISTRY. 

sodium hydroxide, in aqueous or alcoholic solution, to form 
either benzalacetone, C 6 H 5 CH = CH-CO-CH 3 , or dibensalace- 
tojie, C 6 H 5 CH = CH-CO-CH = CHC 6 H 5 . A similar con- 
densation takes place between benzaldehyde and other 
ketones containing a methyl or a methylene (CH 2 ) group 
adjacent to the carbonyl. We may suppose that there is at 
first a simple addition to the benzaldehyde, followed by loss 
of water. Open chain ketones also sometimes condense 
with two molecules of benzaldehyde, giving a hydropyrone * 
derivative. Thus dipropylketone, CH 3 CH 2 CH 2 CO CH 2 CH 2 - 
CH 3 , gives diethyldiphenylhydropyrone, 

C 2 H 5 -CH-CO-CH-C 2 H 5 

! I 

C 6 H 5 - CH - O- CH- C 6 H 5 . 

Cyclic ketones give no similar compounds, but give, instead, 
the simple condensation products. Thus suberone gives 
dibenzalsuberone, 

CH 2 — CH 2 — CH 2 CH 2 

I I 

C 6 H 5 CH = CH CO C = CHC 6 H 5 . 

(Vorlander, Ber. d. ckem. Ges. 30, 2261.) 

These condensations are to be looked upon as closely 
related to the " aldol " condensation (p. 177) on the one 
hand, and to Perkins's synthesis (p. 244) on the other. The 
condensing agent most suitable for a particular case varies 
greatly. Among those which have been used may be 
mentioned, hydrochloric acid, sodium hydroxide, sodium 
ethylate, glacial acetic acid, acetic anhydride, sodium acetate 
and zinc chloride, and sulphuric acid. Such condensations 

* The mother substance, />yrone, has the structure 

CH-CO-CH 

II II ■ 

CH- O-CH 



FORMATION OF MESITYLENE. 191 

have become very useful for synthetical purposes, for the 
determination of the structure of ketones, and for their 
characterization. 

Formation of Mesitylene. — If acetone is mixed with con- 
centrated sulphuric acid, and the mixture distilled after 
standing for some time, from ten to twenty per cent of it 
condenses to mesitylene. 

CH 3 ~c v " fo 

I & 

^>c^ H 

CH 3 

In most, if not in all cases, the condensing agent doubt- 
less unites at first with the aldehyde or ketone to form inter- 
mediate products which react more readily than the original 
compounds, but the nature of the intermediate products 
is usually not clear. The following explanation of the for- 
mation of mesitylene has been given by Michael (/. prak. 
Ch. 60, 132). He supposes that propenyl sulphuric acid, 

8 / C — O — S0 3 H, is at first formed by the addition of sul- 

phuric acid to the acetone, followed by the splitting off of a 
molecule of water. In this compound he supposes the 
central carbon atom to be strongly negative, and the carbon 
atom of the methylene group to be comparatively positive in 
character. This leads to a polymerization which results 
from the combination of each positive carbon atom with a 
negative atom of another molecule, giving the compound, 



192 ORGANIC CHEMISTRY. 

S0 3 H 

I . 
CHo — C — CH„ — C 



, / CH. 



2 ~\S0 3 H 

CH 2 — C — CH 2 

A 
CH 3 . S0 3 H 

This, by loss of sulphuric acid, would give mesitylene. The 
idea that in additions and condensations positive atoms are 
attracted to negative ones, and vice versa, is of very general 
application. Thus, in the addition of hydrocyanic acid 
to aldehydes and ketones, compounds of the structure 

= C ~ AT , and never 01 the structure = C , are 

formed, because the positive hydrogen is attracted by the 
negative oxygen, while the negative cyanogen is attracted 
by the relatively positive carbon. 

Mesityl Oxide, ^ TT 3 >C = CH — CO — CH 3 , and Phorone, 
CH 3 

3 > C = CH-CO-CH = C ' V?, may also be obtained 

by the condensation of acetone under proper conditions. 
Other aliphatic ketones need not be considered here. 

CH 2 -CH, 
Cyclopentanone, | > CO, 

CH 2 -CH, 
CH 2 -CH 2 -CO 
cyclohexanone, | I 

CH,-CH 2 -CH 2 , 

suberone or cycloheptanone, 
CH 2 -CH 2 -CH 2 
I > CO, and other ketones containing rings 

CH 9 -CE,-CH, 



FORMATION OF RINGS. 1 93 

of five, six or seven carbon atoms, are formed by distilling 

CH 2 CH 2 C0 2 H / C H 2 CH 2 C0 2 H 

adipic, | pimehc, CH 2 and 

CH 2 CH 2 C0 2 H, un 2 ^±i 2 ^u a ±i, 

CH 2 CH 2 CH 2 C0 2 H 

suberic, | acids and their derivatives, with 

CH 2 CH 2 CH 2 C0 2 H, 
lime. They are also formed by the condensation of such 
compounds as the diethyl ester of adipic acid by means of 
sodium, and subsequent saponification and decomposition 
of the resulting cyclic ester by " ketonic decomposition " 

(P-35 0- 



CH 2 - 

l 


-CH 2 -C0 2 C 2 H 5 


CH 2 - 


-CH 2 - 


-CO 


1 
CH 2 - 


-CH 2 -C0 2 C 2 H 5 
CH -CH 2 


CH 2 - 


-CH- 


-C0 2 C 2 H 5 




-» | ">CO + C0 2 + CoH 5 OH. 
CH 2 -CH 9 



Formation of Rings. — The fact that reactions of the 
type under consideration take place most readily when 
the resulting rings contain five or six atoms has led to the 
theory that there is an intimate connection between the 
formation of such rings and the nature of the carbon atom. 
If we assume that four atoms combined with a given carbon 
atom are symmetrically arranged in space, the angle be- 
tween the lines joining any two of these atoms with the 
center of the carbon atom will be 109 28'; that is, it will 
correspond to the angle between the lines joining the center 
of a tetrahedron, and two of its corners, or the centers of 
two of its sides. Some years ago Baeyer (Ber. d. chem. Ges. 
r8, 2277) proposed the hypothesis that in certain cases 
atoms may be drawn away from this normal position, but 



194 



ORGANIC CHEMISTRY. 



that there will result a greater or less strain within the 
resulting molecule. This will render the formation of 
molecules in which the departure from the normal position 
is considerable, more difficult, and the resulting compounds 
will be unstable. Now the internal angles of rings consisting 
of three, four, five, six and seven atoms will be : 





Fig. 30. 

The rings of five and six atoms should, therefore, be most 
stable and most easily formed. This conclusion is fully 
justified by a study of cyclic compounds. Not only are 
derivatives of cyclopentane and cyclohexane more easily 
formed and more stable than compounds containing a ring 
with a smaller or larger number of carbon atoms, but mixed 
rings containing five or six atoms, in which one or more of 
the atoms of the ring may be oxygen, nitrogen or sulphur, 
are very common, and many such compounds are important. 
It is also true that a ring containing more than seven or less 
than five carbon atoms has not been prepared by the distilla- 
tion of a calcium salt. 

The cyclic ketones form, in general, the same deriva- 
tives and the same condensation products as the aliphatic 
ketones. 



Oxidation of cyclic ketones. — When cyclic ketones are 
oxidized with nitric acid they give bibasic acids containing 
the same number of carbon atoms. Thus, cyclopentanone, 

CH 2 -CH 2 . . CH 2 -COJi 

> CO, gives glutanc acid, CH 2 < rnw* 

CH,-CH, u±i 2 -cu 2 ±i 



CAMPHOR. 



195 



When oxidized by monopersulphuric acid, S0 2 < 

(Caro's reagent), they give lactones (Baeyer and Villiger,^r. 

d. chem. Ges. 32, 3625 (1899)). Thus, menthone, 

CH 3 

I 
CH 



/ 



\ 



I 



CH 



CH 2 CO 

\ / 

CH 

I 
C 3 H 7 

gives the e-lactone of 2,6 dimethyloctane-3-olic acid, 

CH 3 

I 

C 
/ \ 



CH, 

I 
CH, 

I 
>CH-CH 



CH 2 

I 
CO 

I 

-O 



CH 3 
CH 3 

Camphor, C 10 H 16 O, is a bicyclic ketone having the structure, 
CH 3 
I 



CO 




CR 



CO 



or C 8 H 14 < I . Camphor is a gum obtained from the 
CH 9 



196 ORGANIC CHEMISTRY. 

wood of the camphor tree (Laurus Camphord) by distillation. 

It melts at 176.4 , and boils at 2 09.1 °. It sublimes slowly at 

ordinary temperatures, and condenses in a crystalline form. 

It is optically active, ordinary camphor giving the value 

[ a ] z>== _f-25.4°— a.q, in which q is the amount of the solvent 

in 100 parts of the solution, and a is a factor dependent on 

the nature of the solvent. 

Camphor has been prepared synthetically by the distilla- 

CO IT 
tion of homocamphoric acid, C 8 H 14 < 2 , with lime. 

Cri 2 C(J 2 H 

CHOH 

It gives borneol, C 8 H 14 < I , by reduction, and cam- 

CH 2 
CO TT 
phoric acid, C 8 H 14 < 2 , by oxidation with nitric acid. 

Further oxidation gives camphoronic acid, (trimethyl-tricarb- 
allylic acid), CH.^^^ 

CH 3 J 

CH 3 -C-C0 2 H 
I 
CH 2 -C0 2 H. 

On warming with phosphorus pentoxide camphor loses 
water, and is converted into cymene, /-methyl-isopropyl 
benzene. CH 3 

CH 3 I 

I C 

CH 2 - C - CO // \ 

CH CH 



CH 3 — C — CHg 
I 



-H 2 = 



CH CH 



CH 2 - C - CH 2 ^ 



CH 

/ \ 

CH 3 CH 3 



IRONE. 197 

In this, and in many other cases, camphor and its de- 
rivatives undergo molecular rearrangements which are often 
very puzzling. The laws which govern such rearrange- 
ments are not fully understood, and the impossibility of 
recognizing with certainty when such changes have oc- 
curred has been a fruitful source of error in the study 
of the structure of compounds in the camphor and ter- 
pene group. Partly for this reason, partly because of the 
complex character of the compounds involved, but chiefly, 
perhaps, because for a long time no compound closely 
related to camphor was prepared by synthesis, the deter- 
mination of the structure of camphor has been £ne of 
the most difficult problems in organic chemistry. Fully 
fifty different chemists have worked with the substance 
and contributed to the knowledge of its derivatives, and 
no less than twenty-five formulae for the body have been 
proposed. 

Carone, carvenone, fenchone, citral or geranial, fiulego?ie, 
thujone or tanacetone, and many other compounds isomeric 
with camphor are known. Most of them are not closely 
related to it in structure, and some of them are not 
ketones. 

Irone, CH 3 CH 3 

V 

c 
/ \ 

CH CH-CH = CH-CO-CH 3 , 

II I 

CH CH — CH 3 

\ / 

CH 2 

is found in violet root, and gives to it the pleasant charac- 
teristic odor. A closely related ketone, ionone, 



198 ORGANIC CHEMISTRY. 

CH 3 CH 3 

V 

c 

/ \ 

CH 2 CH-CH == CH-CO-CH 3 , 

I I 

CH CH-CH 3 

CH 

has been prepared synthetically from citral as a starting- 
point. The odor is so nearly identical with that of irone that 
it is manufactured in large amounts for use as an artificial 
perfume. The study of these two bodies forms one of the 
most interesting chapters in the history of organic chemistry 
(Tiemann, Ber. d. chem. Ges. 26, 2675-2708 (1893)). 

Acetophenone, or phenyl-methyl ketone, C 6 H 5 COCH 3 , is 
the simplest aromatic ketone. It may be prepared by 
distilling a mixture of calcium acetate and calcium ben- 

(C 6 H 5 CO/-0) 2 Ca __ . . 

zoate, , * T /' ' „ • The reaction is exactly analo- 

(CH 3 — / CO 0) 2 Ca J 

gous to those for the preparation of acetone and cyclopen- 
tanone. 

A more satisfactory method of preparation, and one which 
is very general in its application, consists in adding alumin- 
ium chloride to a mixture of acetyl chloride and benzene. 
The acetyl chloride combines with the aluminium chloride 
to form a double compound, probably having the structure, 

/0-AlCl 2 
C H 3 C — CI , {Ber. d. chem. Ges. 33, 8 1 5 , 1900; Rec. Trav. 

\C1 
Chim. Pays Bas, 20, 102, (1901)). This double compound 
reacts with the benzene, evolving hydrochloric acid and 



BENZOPHENONE. 1 99 

/0-A1CI 



*2 



forming the compound, CH 3 C — CI . On adding cold 

^C 6 H 5 
water, the last compound is decomposed, giving acetophen- 
one and an aqueous solution of aluminium chloride. 

Acetophenone solidifies at a low temperature, and melts at 
20. 5 . It boils at 202 . 

Acetophenone does not combine with acid sodium sulphite, 
but it forms most of the derivatives and condensation prod- 
ucts which are characteristic of ketones. 

With calcium hypochlorite it gives calcium benzoate and 
chloroform. 



2 C 6 H 5 CO CH 3 + 3Ca0 2 Cl 2 = 2 C 6 H 5 CO CC1 3 + 3Ca(OH) 2 . 
2 C 6 H 5 CO CCI3 + Ca(OH) 2 = Ca(C 6 H 5 C0 2 ) 2 + 2CHCI3. 

A similar decomposition is produced by sodium hypo- 
bromite. Both reactions are analogous to the preparation 
of chloroform from acetone, and are general in their appli- 
cation (pp. 188 and 396). 

Benzophenone, (C 6 H 5 ) 2 CO, is formed by distilling calcium 

//O 
benzoate, or by treating benzoyl chloride, C 6 H 5 C — CI, and 
benzene with aluminium chloride. It melts at 48°, and boils 
at 306. i°. As the compound can be easily obtained pure, 
and boils without decomposition, it is useful for determining 
the accuracy of thermometers. 

Under some conditions of preparation or of treatment, 
benzophenone is formed or is converted into an allotropic 
form, which melts at 2 6°. The cause of the difference 
between the two forms is not clearly understood, but it is 
probably due to a difference in molecular aggregation, and 
not to a difference in structure. The boiling points and 
chemical properties of the two forms are identical, The 



200 ORGANIC CHEMISTRY. 

phenomenon is similar to that of the two forms of sulphur 
which melt at 114 and 120 respectively, with the difference 
that the point of transition for the two forms of benzo- 
phenone lies above the melting point of each, while the 
point of transition for sulphur lies below the melting point 
of each form. 

Beckmann's Rearrangement. — The oxime of benzophenone, 
QH 5 — C — C 6 H 5 

|| , when treated with phosphorus pentachlor- 

N-OH 
ide and then with water, is converted quantitatively into 
benzoic anilide, C 6 H 5 CO — NHC 6 H 5 . This is known as 
"Beckmann's rearrangement," and is general for the ketox- 
imes. It probably takes place in the following steps : 

PC1 5 

C 6 H 5 -C-C 6 H 5 -» C 6 H 5 -C-C 6 H 5 

II II 

N-OH N-Cl 

Benzophenoneoxime. 

->C 6 H 5 -C-C1 ^ C 6 H 5 -C-OH 

II II 

N-C 6 H 5 NC 6 H 5 

-*C 6 H 5 -C = 
I 
NHC 6 H 5 

Benzoic anilide. 

Unsymmetrical derivatives of benzophenone, that is, de- 
rivatives in which the two phenyl groups contain differ- 
ent substituents, generally give oximes which exist in two 
forms. A careful study of many such cases has shown 
that the chemical conduct of the two forms is so nearly iden- 
tical as to justify the belief that each form is a true oxime, 
and that the difference is due to stereoisomerism dependent 



l,2-Df KETONES. 201 

on the nitrogen atom (p. 183). Thus, the oxime of phenyl- 
tolylketone exists in forms represented by the formulas : 

C 6 H 5 -C-C 6 H 4 CH 3 and C 6 H 5 -C-C 6 H 4 CH 8 

II II 

N-OH* HO-N 

When the two oximes are treated with phosphorus penta- 
chloride, each undergoes the " Beckmann rearrangement." 
The first gives benzoic toluide, 

C 6 H 6 -C-C 6 H 4 CH 3 ->C 6 H 5 -C-OH^C 6 H 5 -C = 
II II I 

N-OH N-C 6 H 4 CH 8 NHC 6 H 4 CH 3 . 

The second, on the other hand, gives toluic anilide. 

C 6 H 5 -C-C 6 H 4 CH 3 ->H-0-C-C 6 H 4 CH 8 -*0 = C-C 6 H 4 CH 3 . 

II II I 

HON C 6 H 5 -N C 6 H 5 NH 

Beckmann's rearrangement serves, therefore, to distinguish 
between the two forms. 

When the two groups combined with the carbonyl of 
the ketone differ greatly, the oxime usually exists in only 
one form. Thus, the oxime of acetophenone exists, appar- 

C 6 H 5 — C — CH 3 , 
ently, only in the form, || since it gives, 

HO-N 
= C-CH 3 
by rearrangement, acetanilide, | , and not methyl 

C 6 H 5 NH 
C 6 H 5 -C = 
benzamide, | 

NHCH 3 . 

1,2-DIKETONES, R-CO-CO-R. 

When ketones of the general formula R — CO— CH 2 — R are 
treated with sodium and amyl nitrite, C 5 H n N0 2 , isonitroso- 



202 ORGANIC CHEMISTRY. 

R-CO-C-R . 
ketones, || , are formed. In a similar man- 

N-OH 

ner mono-alkyl derivatives of acetacetic ester, for instance 

CH 3 - CO - CH - C0 2 C 2 H 5 
methyl acetacetic ester, | , give 

CH 3 
isonitroso-ketones on saponification with cold dilute sodium 
hydroxide and subsequent treatment with nitrous acid. 

CH 3 -CO-CH-C0 2 C 2 H 5 + NaOH 

I 
CH 3 

= CH 3 -CO-CH-C0 2 Na + C 2 H 5 OH 

I 

CH 3 
2 CH 3 -CO-CH-C0 2 Na + 2 HN0 2 +H 2 S0 4 

I 

CH 3 
= 2 CH 3 -CO-C-CH 3 + 2 C0 2 + Na 2 S0 4 +2 H 2 

II 
NOH 

Isonitroso methyl- 
ethylketone. 

The reaction involves, in the first place, the " ketonic de- 
composition " characteristic of acetacetic ester and its 
derivatives (p. 351 ). 

CH 3 -CO-CH-C0 2 H = CH 3 -CO-CH 2 -CH 3 . 

I 
CH 3 

In the second place, there is a condensation of the same 
nature as an aldol condensation (p. 177), but with nitrous 
acid in place of an aldehyde. 

ch 3 -co-cTh 2 T-ch 3 

lO i'n-OH 



BENZIL 203 

The isonitroso-ketones are also to be considered as mon- 
oximes of 1,2 -dike tones, and, as such, are decomposed by- 
dilute acids into diketones and salts of hydroxylamine. 

2 CH 3 -CO-C-CH 3 + H 2 S0 4 + 2 H 2 

II 
N-OH 

= 2 CH 3 COCOCH 3 + (NH 4 0) 2 S0 4 . 

Diacetyl or Butanedione, CH 3 COCOCH 3 , is a yellowish 
green oil which boils at 88 . Its vapor is the color of chlo- 
rine. It has a penetrating odor resembling that of quinone 
(p. 209). It dissolves in four parts of water. It forms a 
monoxime which is identical with the isonitroso-methylethyl- 

CH 3 -C = N-OH 
ketone referred to above, and a dioxime, | 

CH 3 -C = N-OH 

For the condensation of butanedion to xyloquinone, see 
p. 211. 

C 6 H 5 -CO 
Benzil, | has already been considered, and the 

C 6 H 5 -CO, 
interest attaching to the stereoisomerism of its oximes was 
spoken of. 

Benzil condenses with o-phenylenediamine, 

/NH 2 1. 

Le 4 \NH 2 2. 

to form ar$-diphenyl qianoxahne, [ I . The 

^^N^ C \C 6 H 5 
reaction is characteristic of ortho-diamines on the one hand, 
and ortho-diketones on the other. Most compounds contain- 

CHO 
ing the group CO — CO — (e.g., glyoxal, | ; oxalic acid, 

CHO 



204 ORGANIC CHEMISTRY. 

C0 2 H CO-CH3 

I ; pyroracemic acid, | ; dioxy tartaric acid, 

C0 9 H C0 9 H 



C(OH) 2 -C0 2 H 

I ; 

C(OH) 2 -C0 2 H 

etc.), react in a similar manner. In all of these cases 
the ready formation of a ring containing six atoms is notice- 
able. I V 

c = o . 

is readily prepared by the 



Phenanthraquinone , 



tr 



=0 



oxidation of phenanthrene. It melts at 205 , and distills 

without decomposition at a temperature above 360 . It 

may be further oxidized to 1,1'diphenic acid, 

C 6 H 4 — C0 2 H 

I ' • 

C 6 H 4 -C0 2 H 

1,3-DIKETONES, (R-CO-CH 2 -CO-R), 
OR /3-DIKETONES. 

1, 3-Diketones, or /?-diketones, are prepared by the con- 
densation of ketones with esters by means of sodium ethylate. 
The reaction takes place readily only with ketones contain- 
ing the group — CO — CH 3 . 

It is supposed that the sodium ethylate forms an addition 
product with the ester : 

/0-C 2 H 5 /OC 2 H 5 

CH 3 -C = +NaOC 2 H 5 = CH 3 -C-OC 2 H 5 . 

\ONa 

This compound then condenses with the ketone: 



i, 3-DIKETONES. 205 



/ ! 0C 9 H ? 



c^-c-locS h 2 j=ch-co-ch 3 

\ I -- I 

CH,-C = CH-CO-CH,. 



ONa 



ONa 



On adding an acid the unsaturated alcohol formed proba- 
bly rearranges, in some cases, to form a 1,3-diketone (p. 139)- 

CH 3 -C = CH-CO-CH 3 = CH 3 -CO-CH -CO-CH 3 . 

1 

QfJ Acetylacetone 

(Pentane 2, 4,dione.) 

In other cases, however, the "enol " or unsaturated alcoholic 
form is undoubtedly retained. The 1,3-diketones containing 
the grouping R — CO — CH 2 — CO — R always have a hydro- 
gen atom which can be replaced by metals ; and in many 
cases such ketones are strong acids, giving a copper salt 
with an aqueous solution of copper acetate and even decom- 
posing carbonates. Formerly it was often assumed that the 
metal in these compounds is united with the carbon atom, 
since compounds in which the alkyl is combined with car- 
bon are formed from them on treatment with alkyl-halides. 

cS;:co> cHNa+cH = i =c5co> cHCH ^ +Nai - 

A careful study of very many related cases makes it more 
probable that the metallic compound is a derivative of the 
" enol " form, and that the reaction in question consists at 
first in the addition of the alkyl- halide to the double union. 

CH 3 -COx = CH 3 -CO\ CH _ 

// / 

CH 3 -C-ONa CH 3 -C-ONa 

\I 

=S:co> CHCH * +Nai - 



206 ORGANIC CHEMISTRY. 

The acid character of the i ,3-diketones is of especial in- 
terest because it has been assumed that true organic acids 

must contain the carboxyl group, — C • A compari- 

son of this group with the " enol " formula of the 1,3 di- 
ketones shows that in each case the hydroxyl group is 
combined with a carbon atom which is doubly united with 
another atom. It has recently been suggested (Vorlander, 
Ber. d. chem. Ges. 34, 1632) that the replaceable hydrogen of 
organic acids, and, indeed, of most inorganic acids as well, 
is usually connected with atoms having a similar grouping. 

Acetylacetone, or 2,4 Pentanedione, CH 3 -CO-CH 2 -CO-CH 3 , 

is formed by the action of sodium, in the form of wire, upon 
a mixture of acetone and acetic ester (see above). It is a 
colorless liquid which boils at 137 . The copper salt, 

/CH 3 -CO\ \ 

^LH c u? i s precipitated on adding a solution 



\CH 3 C— O 

of copper acetate to its aqueous solution. 

The oxime of acetylacetone loses water as soon as formed, 
and condenses to a-y-dimethylisoxazole, 

CH-C-CH3 

II II 

CH 3 -C N 

\ / 
O 

a reaction characteristic of the /3-diketones. 

With phenyl hydrazine, C 6 H 5 NHNH 2 , it gives, in a simi- 
lar manner, i-phenyl-^^-dimethyl pyrazole, 

C 6 H 5 

I 

N 

/ \ 

CH 3 -C N 

II II 

CH C-CH* 



ACETONYLACETONE. 207 

Similar reactions, resulting in heterocyclic compounds, 
that is, compounds with rings containing atoms of two or 
more kinds, are frequent and important. 

PIT CC\ 

Dihydroresorcinof, CH 2 < r , TT 2 ^_ > CH 2 , or 1,3 Cyclo- 
Cri 2 — CO 

hexanedione, has already been quite fully considered. Unlike 

the open chain, 1,3-diketones, it forms a dioxime and a 

normal phenylhydrazone. It would seem that the cyclic 

structure prevents, in this case, the formation of an isoxazole 

or pyrazole compound. 

CH 2 -CO-R 
1,4-DIKETONES, 1 

CH 2 -CO-R 

CH 2 -CO-CH 3 
Acetonylacetone or 2,5-Hexanedione, | , is the 

CH 2 -CO-CH 3 

simplest of the aliphatic 1,4, or y-diketones. When sodium 
acetacetic ester is treated with iodine, diacetylsuccinic ester 
is formed. 

2 C 2 H 5 CO-CH C 2 H 5 C0 2 -CH-CH-C0 2 C 2 H 5 

II +2 1= || 

CH 3 -C-ONa CH3-CO CO-CH 3 

+ 2NaI 

The diacetylsuccinic ester gives, on saponification with di- 
lute sodium hydroxide, acetonylacetone. 

CH 3 -CO-CH-C0 2 C 2 H 5 

I +2NaOH + 2 H 2 

CH 3 -CO-CH-C0 2 C 2 H 5 

CH 3 -CO-CH 9 
= 1+2 NaHCO, + 2 C 2 H 5 OH. 

CH 3 -CO-CH 2 

Acetonylacetone boils at 194 , and is miscible with water, 



208 ORGANIC CHEMISTRY. 

alcohol, or ether in all proportions. It is insoluble in a con- 
centrated solution of potassium hydroxide or potassium car- 
bonate. The last fact indicates that it is a true ketone, and 
distinguishes it sharply from the i ,3-diketones, which pass 
readily into the " enol " form (see p. 205). 

When distilled with zinc chloride acetonylacetone gives 
2,5 dimethylfurane (or dimethylfurfurane)> 

O 

/ \ 
CH 3 — C C — CH 3 . 

II II 

CH-CH 

With phosphorus pentasulphide it gives 2 ^-dimethylthio- 

furane (or dimethylthiophefie)^ 

S 

/ \ 
CH 3 -C C-CH 3 . 

II II 

CH-CH 

With alcoholic ammonia it gives 2,5-dimethylazole (or 
dimethvlpyrrol), 

NH 

/ \ 
C H 3 — C C — C H 3# 

II II 

CH- CH 

Acetonylacetone forms a dioxime and a diphenylhydra- 
zone. 

An examination of the statements of the last few pages 
reveals the fact that each class of aliphatic diketones forms 
cyclic compounds peculiar to itself, but that in each case the 
cyclic compounds which are most characteristic and most 
easily formed contain a ring of five atoms. 



QUINONES. 209 

QUINONES. 

In the aromatic series there is a peculiar class of 1,4 di- 
ketones known as quinones. These bodies differ from ordinary 
ketones in so many ways that for a long time another struc- 
ture was often ascribed to them. The work of Nef and of 
others has, however, placed their structure as ketones beyond 
reasonable doubt. 

Quinone, CO 

/ \ 
CH CH 

II II , 

CH CH 

\ / 

CO 

is most easily prepared by the oxidation of aniline, C 6 H 5 NH 2 , 

by a mixture of dilute sulphuric acid and sodium pyro- 

chromate. It is also formed by the oxidation of hydro- 

nTT OHi . . . „ TT OH 1 

quinone, C 6 H 4 < , p-aminophenol, C 6 H 4 < , and 

OH 4 JN H 2 4 

p-diaminobenzene (p-phenylenediamine), C 6 H 4 < 2 . All 

MH 2 4 

of these methods are general in their application, and may 

be used for the preparation of other quinones. 

Quinone crystallizes in yellow prisms or needles which 

melt at 11 6°. It has a peculiar penetrating odor resembling 

that of chlorine. It acts, in many cases, as an oxidizing 

agent, and is itself reduced to hydroquinone. At a time 

when very few compounds intermediate between benzene and 

cyclohexane were known, the close relation between quinone 

and hydroquinone as well as the other properties of quinone, 

especially as an oxidizing agent, led most chemists to favor 

Graebe's peroxide formula for the body. 



210 ORGANIC CHEMISTRY. 



c 




CH i CH 
O 

I 


CH V CH 


x c 7 





(Zeit.f. Chem. 3, 39 (1867)). 

The following facts, however, indicate that it is a diketone : 
It adds directly two or four atoms of chlorine or bromine, 

forming such compounds as, 

CO CO 

/ \ / \ 

CH CHC1 CHBr CHBr 

II I and I I 

CH CHC1 CHBr CHBr 

\ / \ / 

CO CO 

It condenses with hydroxylamine to form a monoxime and 
a dioxime, 

NOH NOH 

II II 

c c 

/ \ / \ 

CH CH and CH CH 

II II II II • 

CH CH CH CH 

\ / \ / 

CO c 

II 

NOH 

Quinone monoxime is also formed by the action of nitrous 
acid on phenol. 

C 6 H 5 OH + HN0 2 = C 6 H 4 ^° H + H 2 0. 



ANTHRAQUINONE. 2 I I 

On account of this method of formation the compound 

NO 

is called p-nitrosophenol, and the formula, C 6 H 4 < , 

OH 

is ascribed to it. . Since it gives with hydroxylamine the 

.. . ^ TT ^N-OH , ; . 

dioxime, C 6 H 4 . , the formula representing it as an 

oxime seems to be more probable. 

p-Xyloquinone is formed by warming butanedione (p. 203) 
with a dilute solution of sodium hydroxide : 

CH 3 C - CO - CH 

r 11 ". 

o 1 h, 1 

CH-CO-C-CH3 

^CH 3 i. 

It gives by reduction dihydroxy-p-xylene, C 6 H 2 < r , TT 

OH 5. 

CO 

Anthraquinone, f TT IT J? 1S formed easily by the direct 

CO 

oxidation of anthracene with chromic acid. Anthraquinone 
is also formed by the following reactions which demonstrate 
its structure. 

Phthalic anhydride when treated with benzene and alu- 
minium chloride gives o-benzoylbenzoic acid : 

C 6 H 4 < ££ > O + C 6 H 6 + AICI3 = C 6 H 4 < £° ~ CeH5 + AICI3. 

This acid on treatment with phosphorus pentachloride 
gives anthraquinone : 

CeH4< CO H 5 + PC1 5 = C 6 H 4<^>C 6 H 4 +2HCH-POCl 3 



212 ORG A 'NIC CHEMISTRY. 

In a similar manner bromanthraquinone (see p. 117), 

CO 
C 6 H 3 Br< c() >C 6 H 4 , 

may be obtained, starting with bromphthalic anhydride. 
At 160 , with potassium hydroxide, bromanthraquinone 

CO 

yields hydroxyanthraquinone, C 6 H 3 (OH) < > C 6 H 4 , and 

this, by oxidation with nitric acid, gives phthalic acid. 
Since phthalic acid is an ortho compound, and since the 
benzene nucleus which came from the bromphthalic acid 
must be the one destroyed by the oxidation, it follows that 
the two carbonyl groups are combined with adjacent carbon 
atoms in each of the benzene nuclei of. anthraquinone. 

Anthraquinone crystallizes in yellow needles. It melts at 
2 73 and boils at 380 . 

Alizarin. — Anthraquinone is of especial interest because 
of its relation to alizarin, the coloring matter of madder root 
which is used in dyeing for the color known as " Turkey red." 

In 1868 Graebe and Liebermann discovered that by 
distilling alizarin with zinc dust anthracene is formed. This 
discovery formed the basis of further work, which finally led 
to the commercial manufacture of alizarin by the following 
steps : 

Anthracene, from coal-tar, is first oxidized to anthra- 
quinone. When this is heated with fuming sulphuric acid, 

CO 

anthraquinonesulphonic acid, C 6 H 4 < > C 6 H 3 S0 3 H, is 

formed ; and when this is heated with sodium hydroxide and 
potassium chlorate the sulphonic acid group is replaced by 
hydroxyl and an adjacent hydrogen atom is also oxidized to 
hydroxyl, giving alizarin, 



ALIZARIN. 



213 



OH 



OH 



In madder root alizarin is found as a glucoside, C 20 H 22 O u , 
which is decomposed by ferments or by dilute acids or 
alkalies. 

QoH 22 O u = C 14 H 8 4 + C 6 H 12 6 + H 2 0. 

Alizarin crystallizes in red needles. It melts at 290 , and 
boils at 43 o°. It dissolves in sodium or potassium hydrox- 
ide, giving a deep red solution from which it is repre- 
cipitated by carbon dioxide. It forms a not very sensitive 
indicator for acidimetry. It is a red dye with aluminium 
mordants,* a violet dye with a ferric salt as a mordant, and 
a granite brown with a chromium salt. 

The value of the alizarin manufactured during 1880 is 
given as $8,000,000. It is estimated that the manufacture 
of the same amount of alizarin from madder root would have 
cost $28, 000, 000. t In other words, in the manufacture of 
this single dyestuff an annual Saving of $20,000,000 is 
effected by a method of manufacture based on the study of 
the structure of alizarin. 

Several other dihydroxyanthraquinones are known. Of 
these, all having the hydroxyl groups in the ortho position 
toward each other are dyestuff s. 



* A " mordant " is an inorganic compound which combines with a dyestuff to form 
an insoluble compound, called a " lake." 

t Heinzerling, Abriss der che7iiischeu Techtiologie , S. 164. 



214 



ORGANIC CHEMISTRY. 



The derivatives of anthracene * are best classified by the 
following scheme, in which the numerals are given the 
preference. a' x a 




Unfortunately, actual usage frequently does not conform 
to this scheme, especially in naming those derivatives with 
substituents in positions 9 and 10. 

The following are the more interesting of the derivatives 

of anthracene : — 

CH 
Anthrol, C 6 H 4 < | > C 6 H 3 (OH), 1 and 2 or a and /3. 
CH 
C(OH) 
Anthranol, C fi H 4 < | > C 6 H 4 . 

CH 

Hydroanthranol, C 6 H 4 < CH > C e H 4- 

CO 

Anthranone, C 6 H 4 < > C 6 H 4 (isomeric with anthranol). 

C(OH) 
Anthrahydroquinone, C 6 H 4 < | > C 6 H 4 . 

C(OH) 
Dioxyanthracene,f \ qh 

Rufol, flavol, |c 6 H 3 (OH)< | >C 6 H 3 (OH). 

Crysazol, ) ^^ 

CO 
Anthraquinone, C 6 H 4 < > C 6 H 4 . 

CO 
Anthraquinone, monosulphonic acid, C 6 H 4 <£q> C 6 H 3 S0 3 H. 

CO 
Oxyanthraquinone,| C 6 H 4 < co > C 6 H 3 (OH) (1 and 2). 

* While a discussion of the derivatives of anthracene does not logically belong here, 
this seems to be, practically, the best place for its introduction, 
t More properly dihydroxyanthracene. 
$ Or hydroxyanthraquinone. 



DERIVATIVES OF THE ANTHRACENE. 215 



C 6 H 4 <™>C H 2 (OH) 2 , 

and 
C 6 H 3 (OH)<™>C 6 H 3 (OH). 



Flavopurpurin (1,2,6), \ C 8 H 8 (OH)< C() >CH 2 (OH) s 



Dioxyanthraquinone, 
Alizarin (1,2), 
Purpuroxanthin (1,3), 
Quinazarin (1,4), 
Anthrarufin (1,5 ), t 
Crysazin (1,6) ? 
Benzdioxyanthraquinone (1,7) 
Hystarin (2,3), 
Anthraflavinic acid (2,6), 
Isoanthraflavinic acid (2,y), 

Trioxyanthraquinone, 

Purpurin (1,2,4), C 6 H 4 <™> CH(OH) 31 

Oxyanthrarufin (1,2,5), 1 „ 

Flavopurpurin (1,2,6), 
Anthrapurpurin (1,2,7). 

The list might be greatly extended to include nitro com- 
pounds, amines, nitroso derivatives, and many other bodies 
which are known. 

General Methods of Preparing Aldehydes. 

1. Oxidation of primary alcohols : 

R-CH 2 OH + = R-C-H + H 2 0. 

2. Distillation of a calcium salt of an acid mixed with 
calcium formate : 

(R-C0 2 ) 2 Ca + (HC0 2 ) 2 Ca- 2 R-C-H + 2CaC0 3 . 

3. By boiling compounds containing the group — CHC1 2 
with water or with water and lead oxide: 

R-CHC1 2 + H 2 = R-C-H + 2 HC1. 



2l6 ORGANIC CHEMISTRY. 

Of less importance, but still general in character, are the 
following : 

4. By the action of nascent hydrogen on the chloride of 
an acid : 

R-C-C1+2H = R-C-H + HC1. 

5. By treating with an acid the sodium salt of a nitro- 
paraffin having the nitro group attached to an end carbon 
atom : 

2 R-CH = N-ONa-f-2HCl 

= 2 R-C-H + 2 NaCl + N 2 + H 2 0. 

6. By warming a-hydroxy acids, containing the group 
R— CH(OH)C0 2 H, with lead peroxide and dilute sulphuric 
acid: 

R-CH(OH)C0 2 H + Pb0 2 + H 2 S0 4 

= R-C-H + PbS0 4 +C0 2 +2 H 2 0. 

7. Treatment of a hydrocarbon of the aromatic series 
with chromyl chloride, followed by water : 



R-CH 3 + 2Cr0 2 Cl 2 = R-CH 



/0-CrCl 2 OH 
\0-CrCl 2 OH 



General Methods of Preparing Ketones. 
1. Oxidation of secondary alcohols : 

^>CHOH-r-0 = ^>CO + H 2 0. 



GENERAL METHODS OF PREPARING KETONES. 217 

2. Distilling calcium salts of acids: 

t':co:> Ca =R'> co+caco *- 

3. By boiling compounds containing the group , CC1 2 

R / 

with water or water and lead oxide : 



;>ci 2 +h 2 o = „, ;co-f2Hci. 



J,>C1 2 +H 2 = | / ) 

4. By treating the chloride of an acid with a zinc alkyl : 



R / /O-ZnR' 

R-COCl + Zn^ . _ = R-C-R' 

K \C1 

/O-ZnR' 

R-C-R' + R-COCl = 2 R-COR' + ZnCl,, 

\C1 

or, 

/O-ZnR' OH 

R-C-R' +H 2 = R-CO-R'+Zn' +RH. 

\ CI U 

5. By treatment of the chloride of an acid with aluminium 
chloride and an aromatic hydrocarbon (p. 198). 

6. By the " ketonic " decomposition of compounds of the 
type of acetacetic ester (p. 351) : 
R-C0-CH 2 C0 2 C 2 H 5 + HC1 + H 2 

= R-CO-CH 8 +C0 2 + C 2 H 5 OH + HCl. 

Of less importance : 

7. Treatment of the metallic salt of a secondary nitro 
derivative with an acid : 

2^ / >C = N( ONa +2HCl = 2^>CO+2NaCl+N 2 0+H 2 0. 

8. By warming an a-hydroxy acid containing the group 

~D y OTT 

,> C ^ TJ . with lead peroxide and sulphuric acid : 



218 ORGANIC CHEMISTRY. 



R ,>c; caH +Pbo 2 +H 2 so 4 



= ^,>CO + CO.,+PbS0 4 +2 H„0. 

JK. 



General Characteristics of Aldehydes and Ketones. 

i. Aldehydes maybe reduced to primary alcohols, ketones 
to secondary alcohols. 

2. Aldehydes may be oxidized to monobasic acids con- 
taining the same number of carbon atoms, open-chain ketones 
to acids containing a smaller number of carbon atoms, and 
cyclic ketones to bibasic acids containing the same number 
of carbon atoms. 

3. Aldehydes polymerize easily, ketones do not. 

4. Both aldehydes and ketones condense readily with 
themselves and with other compounds in many ways that 
are useful for synthetic purposes. 

5. Treatment with phosphorus pentachloride replaces the 
oxygen of either an aldehyde or a ketone with two chlorine 
atoms. 

6. With hydroxylamine each forms oximes, and with 
phenylhydrazine, C 6 H 5 NHNH 2 , semicarbazine, NH 2 — NH — 
CO — NH 2 , etc., each forms phenylhydrazones, semicarba- 
zones, etc. 

7. With hydrocyanic acid each forms cyanhydrins, or 
nitriles of a-hydroxy acids, 

/OH /OH 

R-C-CN, or R-C-CN. 
\H \R' 

8. Aldehydes reduce a cold ammoniacal solution of silver 
nitrate. They also redden a very dilute cold solution of a 
fuchsine salt which has been decolorized by sulphurous 
acid. Ketones do not give these reactions. 



LABORATORY EXERCISES. 219 

9. Some aldehydes, especially those of the aromatic series, 
are converted by caustic potash into an alcohol and a salt of 
an acid. 

2 C 6 H s C-H+-KOH = C 6 H 5 C0 2 K + C 6 H 5 CH 2 OH. 

Potassium Benzyl 

benzoate. alcohol. 

Many aldehydes, on the other hand, are converted by 
alkalies into uncrystallizable resins. 

Laboratory Exercises. 

Preparation of the following substances : 

1. Formaldehyde 

2. Acetaldehyde ; paraldehyde ; metaldehyde ; aldehyde am- 
monia. 

3. Ethylidene acetacetic ester. Knoevenagel, Ann. Chem. 
(Liebig), 281, 104. By a misprint 3.4 g. acetaldehyde is given in- 
stead of 34 g. 



4- 


Aldol and crotonic aldehyde. 


5- 


Benzaldehyde. 


6. 


Synbenzaldoxime and antibenzaldoxime. 


7- 


Benzoin and benzil. 


8. 


Acetoxime. 


9- 


Benzalacetone and dibenzalacetone. 


10. 


Propionic and butyric acids from 4-heptanone. 


11. 


Camphoric acid. 


12. 


Acetophenone. 


i3- 


Benzophenone. 


14. 


Oxime of benzophenone ; Beckmann's re-arrangement 


iS- 


Diacetyl. 


16. 


Acetylacetone. 


17- 


Benzoquinone. 


18. 


Alizarin. 



220 ORGANIC CHEMISTRY. 



CHAPTER XIII. 
ACIDS. 

Structure. — In empirical formula all of the common mono- 
basic organic acids differ from the hydrocarbons containing 
the same number of carbon atoms in that they contain two 
oxygen atoms in place of two hydrogen atoms. Thus, from 
methane, CH 4 , we have formic acid, CH 2 2 , from ethane we 
have acetic acid, C 2 H 4 2 , from toluene, C 7 H 8 , we have benzoic 
acid, C 7 H 6 2 . 

Many sodium salts of organic acids, when mixed with soda 
lime and distilled, give a hydrocarbon containing one carbon 
atom less than the acid, the change from the acid to the hy- 
drocarbon consisting simply in the loss of carbon dioxide : 

C 2 H 3 2 Na + NaOH = CH 4 + Na 2 CO s 

Sodium acetate. Methane. 

Many acids can be prepared from monohalogen deriva- 
tives of hydrocarbons by reactions of which the following 
are typical : 

C 2 H 5 Br + KCN = C 2 H 5 CN + KBr 

Ethyl bromide. Ethyl cyanide. 

C 2 H 5 CN + HC1 + 2H 2 = C 3 H 6 2 +NH 4 C1 

Propionic acid. 

A little consideration of these facts leads to the conclusion 
that organic acids may be considered as substitution products 
in which the univalent group CO a H, called carbaxyt, replaces 
one hydrogen atom of a hydrocarbon or other carbon com- 
pound. According to this view acetic acid is to be writ- 



DEFINITION OF AN ACID. 221 



ten CH 3 C0 2 H, propionic acid, C 2 H 5 C0 2 H, benzoic acid, 
C 6 H 5 C0 2 H. 

The further structure of the carboxyl group is best 
shown by the conduct of acids when treated with phos- 
phorus pentachloride. 

CH 8 Cq 2 H + PCl 6 = CH 8 C0C1 + P0C1 8 +HC1 

Acetic acid. Acetyl chloride. 

In almost all cases this treatment results in the exchange 
of an oxygen and hydrogen atom of the acid for the univa- 
lent chlorine atom. This indicates the presence of a hy- 
droxyl group, and gives the structure — CO. OH, for the 
carboxyl group. The relation of the second oxygen atom 

cannot be well expressed other than thus, — C — O — H. 

Definition of an Acid. — In accordance with the ideas 
now most generally accepted, an acid is a compound which 
is dissociated, or ionized in an aqueous solution with the 
formation of hydrogen ions. From a previous discussion 
(p. 143) it seems probable that many substances not prop- 
erly called acids undergo some dissociation of this sort, and 
that we may have all degrees of ionization, from that of 
aliphatic alcohols, which dissociate less than water, and 
whose sodium derivatives are, therefore, decomposed by 
water, to that of trichloracetic and oxalic acids whose disso- 
ciation approaches, or even exceeds, that of some mineral 
acids. With our present conception of acids it seems to be 
a little difficult to frame a definition of organic acids or, in- 
deed, of acids in general, which is not more or less arbitrary. 
Perhaps as satisfactory a definition as we can give is to say 
that an acid is a substance which ionizes in an aqueous solu- 
tion so far as to increase the number of hydrogen ions nor- 
mally present in pure water. Under this definition ethyl 



222 



ORGANIC CHEMISTRY. 



alcohol and similar compounds are not acids, although they 
form such compounds as C 2 H 5 ONa. Phenol, C 6 H 5 OH, on 
the other hand, is an acid, since its aqueous solution contains 
a sufficient number of hydrogen ions to give it a measurable 
conductivity (p. 144). While considerations of this sort 
lead us to include among the organic acids a few compounds 
which do not contain the carboxyl group, almost all such 
acids do contain that group. 



FATTY ACIDS, C w H 2n 2 . 







Melting 


Boiling 






Point. 


Point. 


Formic acid 


H — C0 2 H 


8.5 


IOI° 


Acetic acid 


CH 3 C0 2 H 


16.7° 


120 


Propionic acid 


C 2 H 5 C0 2 H 


-23° 


140.9 


Butyric acid 


GH^CH^CHtjCOtjH 


o° 


162. 5 


Isobutyric acid 


Cg3 >CHC02 H 


-79° 


153-5° 


Valeric acid 


CH 3 (CH 2 ) 3 C0 2 H 


— 18 


1 86° 


Isovaleric acid 


gg 3 >CHCH 2 C0 2 H 


-Si° 


176.3 


2-Methylbutanoic acid 


CH 3 — CH 2 — CH — C0 2 H 

CH 3 
CH 3X 




I77 ° 


Dimethylpropanoic acid 


CH,- C — C0 2 H 

CHg/ 


35-5° 


163. 7 


Caproic acid 


CH s (CH 2 ) 4 C0 2 H 


- i-S° 


205 ° 


Isocaproic acid 


£§ 3 > CHCH 2 CH 2 C0 2 H 





20I° 


Oenanthylic acid 


CH 3 (CH 2 ) 3 C0 2 H 


- io. S ° 


224° 


Caprylic acid 


CH 3 (CH 2 ) 6 C0 2 H 


+ 16.5 


2 3 6° 


Pelargonic acid 


CH 3 (CH 2 ) 7 C0 2 H 


12.5 


253° 


Capric acid 


CH 3 (CH 2 ) s C0 2 H 


3i° 


270 






At 100 mm. 200 


Undecylic acid 


CH 3 (CH 2 ) 9 C0 2 H 


28.5 ' 


' 212.5° 


Laurie acid 


CH 3 (CH 2 )^qC0 2 H 


43-6° 


225° 


Tridecylic acid 


CH 3 (CH 2 ) n C0 2 H 


40.5° 


2 3 6° 


Myristic acid 


CH 3 (CH 2 ) 12 C0 2 H 


53.8° 


250° 


Pentadecylic acid 


CH 3 (CH 2 ) 13 C0 2 H 


5i° 


257° 


Palmitic acid 


CH 3 (CH 2 ) 14 C0 2 H 


62 


271.5° 


Margaric acid 


CH 3 (CH 2 ) ir ,C0 2 H 


59-8° 


2270 


Stearic acid 


CH 3 (CH 2 ) 16 C0 2 H 


69.2 


291 


Nondecylic acid 


CH 3 (CH 2 ) 17 C0 2 H 


66.5° 


298 


Arachidic acid 


CH 3 (CH 2 ) 18 C0 2 H 


75° 





Behenic acid 


CH 3 (CH 2 ) 20 CO 2 H 


83° 






FORMIC ACID. 22 3 

Lignoceric acid CH 3 (CH 2 ) 22 C0 2 H 80.5° 

Hyenicacid CH,(CH 2 ) 23 C0 2 H 78 

Ceroticacid CH,(CH 2 ) 25 C0 2 H (?) 78 

Melissicacid CH 3 (CH 2 ) 28 C0 2 H 90 

Dicetyl acetic acid £«**»> CHC0 2 H 70 

Formic Acid, H — C0 2 H (methanoic acid). — The first acid 
of the series is formed : 

1. By the oxidation of formaldehyde by means of hydrogen 
peroxide in alkaline solution : 

H 2 C = + H 2 2 -f-NaOH = H-C-ONa- 2 H 2 

It need hardly be remarked that the relation between an 
acid and its salt is so close that the preparation of the salt 
of an acid is often spoken of as a preparation of the acid. 

The oxidation consists, as has been pointed out, in the in- 
troduction of an oxygen atom between the carbon and hy- 
drogen atoms. Formic acid may also be formed by the 
direct oxidation of methyl alcohol, 

2. By the action of hydrochloric acid or an alkali on 
hydrocyanic acid : 

HCN + HC1 + 2H 2 = HC0 2 H + NH 4 C1 
HCN + KOH + H 2 = HC0 2 K -f NH 3 

3. By the absorption of moist carbon monoxide by soda 
lime at i90°-2 2o°: 

CO + NaOH = H - C0 2 Na 

Carbon monoxide may be looked upon as the anhydride of 
formic acid. 

4. By the reduction of moist carbon dioxide by metallic 
potassium, or of ammonium carbonate by sodium amalgam : 



2 K+2C0 2 + H 2 = HC0 2 K + HKCO 
(NH 4 ) 2 C0 3 + 2 Na = HC0 2 Na + 2NH 3 - 



-f-NaOH 



224 ORGANIC CHEMISTRY. 

5 . By the action of alcoholic potash on chloroform : 

CHCI3+4KOH = HC0 2 K+ 3 KC1 + 2H 2 

The similarity between this reaction and the formation of 
aldehydes and ketones from dihalogen derivatives of hydro- 
carbons should be noticed. 

6. Formic acid is practically prepared by heating oxalic 
acid with glycerol, the decomposition taking place best at a 
temperature of 115 — 125° The formic acid formed by the 
decomposition of the oxalic acid reacts at first with the gly- 
cerol to form monoformin. 

*° 
CH 2 OH CH 2 -0-C-H 

C0 2 H I I 

I + CHOH = CHOH + C0 2 + H 2 

C0 2 H I I 

CH 2 OH CH 2 OH 

Oxalic acid. Monoformin, 

The monoformin then reacts with, or is saponified by the 
water, giving formic acid, which distills, and regenerating the 
glycerol : 

C 3 H 5 (OH) 2 (CH0 2 ) + H 2 = C 3 H 5 (OH) 3 + H 2 C0 2 

The formic acid obtained in this manner contains water ; 
by fractional distillation it may be concentrated till an acid 
of 77.5 per cent, boiling at 107.1 , is obtained. A stronger 
acid can be prepared by dissolving anhydrous oxalic acid 
in such an acid. On cooling, the oxalic acid crystallizes with 
water of crystallization leaving formic acid nearly free from 
water. Another method consists in treating dry lead for- 
mate, (CH0 2 ) 2 Pb, with hydrogen sulphide. 

Pure formic acid solidifies at a low temperature, and melts 
at 8. 5 . It boils at 101 . 

Formic acid is a strong acid. From the electrical con- 



ACETIC ACID. 225 

ductivity, K = 0.0214, while for acetic acid K = 0.00180 
(p. 49). 

Formic acid produces painful blisters on the skin. It is 
secreted by some insects, and is, apparently, the cause of the 
irritation produced by the sting of the bee. The name is 
derived from the fact that it was first obtained by the distil- 
lation of ants. 

When sodium formate is heated with sodium hydroxide 
hydrogen is evolved. 

NaCH0 2 + NaOH = Na 2 C0 3 + H 2 . 

When the acid is heated with concentrated sulphuric acid 
it is decomposed with evolution of carbon monoxide. 

CH 2 2 = CO + H 2 0. 

Formates of many of the metals are known. The lead 
and copper salts crystallize well, and are used for the pur- 
pose of purification. 

From its structure formic acid may be considered in some 

sense as an aldehyde, H — O — C — H. In accordance with 
this structure it is a strong reducing agent, an ammoniacal 
solution of silver nitrate being reduced by it to metallic sil- 
ver, and mercuric chloride being reduced to mercurous chlo- 
ride and then to metallic mercury. These reactions are used 
for its qualitative detection. 

Acetic Acid, CH 3 C0 2 H (ethanoic acid). — Acetic acid is 
practically prepared by the oxidation of alcohol, or by the 
destructive distillation of wood. The impure acid obtained 
in the second manner is sometimes called pyroligneous acid. 

The oxidation of alcohol, while it can be effected by 
means of chromic acid and other oxidizing agents, is prac- 
tically carried out by a process of fermentation. The micro- 



226 ORGANIC CHEMISTRY. 

organism known as mycoderma aceti, or " mother of vinegar," 
is the effective agent ; but, unlike the alcoholic fermentation, 
oxygen must also be present. In the slow vinegar process, 
cider, wine, or a dilute alcohol resulting from the fermenta- 
tion of a malt liquor, is allowed to stand for some weeks in 
casks which are sufficiently open to allow a very slow circula- 
tion of air. 

In the " quick vinegar process " dilute alcohol of 6 to 10 
per cent is allowed to trickle slowly over beech shavings 
which have been previously inoculated with the living fer- 
ment. A slow current of air through the apparatus used is 
secured by suitable openings and by the fact that the reac- 
tion is accompanied by an evolution of heat. The temper- 
ature must be regulated, 35 being most suitable. 

The acetic acid prepared as described is mostly used as 
vinegar. A stronger acetic acid is obtained usually from the 
mixture of substances formed by the destructive distillation 
of wood. Oak, beech, and similar woods of comparatively 
young growth (trees 3 to 4 inches in diameter) are most suit- 
able for the purpose ; and, to obtain an acid which can be 
readily purified, only a moderate temperature (i9o°-2o5°) 
should be employed. 

By fractional distillation a dilute acetic acid can be con- 
centrated, and an acid nearly free from water can finally be 
obtained. Practically, however, a dilute acid is converted 
into its calcium or sodium salt, the water is evaporated, and 
the dry salt is decomposed with hydrochloric or sulphuric 
acid. 

Pure acetic acid melts at 16.7 , and boils at 120 . It has 
a specific gravity of 1.055 at 15 . The addition of water 
increases the specific gravity to a maximum of 1.075 ^ or an 
acid of 80 per cent. This corresponds approximately to 
C 2 H 4 2 + H 2 0, and may be due to the formation of the 



DECOMPOSITIONS. 227 

compound CH 3 — C(OH) 3 . Further addition of water causes 
the specific gravity to decrease again. An acid of about 43 
per cent has the same specific gravity as the pure acid, and 
between these limits each specific gravity corresponds to 
acids of two degrees of concentration. In a given case, 
whether a strong or weak acid is in hand, can be deter- 
mined by adding a little water and noting whether the spe- 
cific gravity increases or decreases. 

Salts of Acetic Acid. — Many acetates are known, the most 
interesting being lead acetate, Pb(C 2 H 3 2 ) 2 + 3H 2 0, or sugar 
of lead ; a basic lead acetate, Pb(OH)C 2 H 3 2 , or PbO + 
Pb(C 2 H 3 2 ) 2 H-H 2 0, formed by dissolving litharge in a solu- 
tion of lead acetate, and much used to clarify sugar solu- 
tions ; calcium acetate, Ca(C 2 H 3 2 ) 2 -f- H 2 ; and sodium 
acetate, NaC 2 H 3 2 + 3 H 2 0. 

Acid Salts of Acetic Acid. — Sodium and potassium also 
form with acetic acid, acid salts, as KH(C 2 H 3 2 ) 2 and KH 2 
(C 2 H 3 2 ) 3 . Whether the acetic acid of such salts is to be 
looked upon as similar to water of crystallization, or whether 
the salt is to be considered as derived from a polymer of 
acetic acid, is, at present, only a matter for speculation. It 
may, indeed, be questioned whether there is any real differ- 
ence between the two views. It is interesting to notice, in 
this connection, that at temperatures slightly above its boil- 
ing point the vapor density of acetic acid is abnormally high, 
indicating the presence in the vapor of molecular aggregations 
or of a polymeric form. 

Decompositions. — By heating sodium acetate with soda- 
lime methane is formed, and by the electrolysis of acetic acid 
ethane and carbon dioxide are evolved at the anode, and hy- 
drogen at the kathode. The significance of these reactions 



228 ORGANIC CHEMISTRY. 

in their relation to the structure of acetic acid has been dis- 
cussed. 

Uses. — Dilute acetic acid is used chiefly in the form of 
vinegar. Since there is no tax upon it, it is used to a limited 
extent in place of alcohol for the preparation of fluid extracts 
of some drugs, especially those containing alkaloids. The 
aluminium, iron, and chromium salts are used as mordants in 
dyeing and calico printing. Acetic acid and iron are used 
for the reduction of nitro compounds in the manufacture of 
artificial colors. 

Propionic Acid, CH 3 CH 2 C0 2 H (propanoic acid), can be ob- 
tained by the oxidation of normal propyl alcohol, CH 3 CH 2 
CH 2 OH. It may also be prepared from ethyl cyanide. 
When ethyl alcohol is mixed with concentrated sulphuric acid 
it is partly converted into ethyl sulphuric acid, C 2 H 5 HS0 4 . 
On diluting and neutralizing with calcium carbonate the 
calcium salt of this acid remains in solution, while most 
of the sulphuric acid is deposited as insoluble calcium sul- 
phate. By precipitating the filtrate exactly with sodium or 
potassium carbonate the sodium or potassium salt is formed, 
and may be obtained dry by evaporating the faintly alkaline 
solution, an acid solution being relatively unstable and de- 
composing with the formation of acid potassium sulphate and 
alcohol. When the dry potassium salt is mixed with potas- 
sium cyanide and distilled, ethyl cyanide is formed. 

KC 2 H 5 S0 4 + KCN = K 2 S0 4 + C 2 H 5 CN. 

Ethyl cyanide may also be prepared by dissolving potas- 
sium cyanide in its own weight of water, adding the calcu- 
lated amount of ethyl bromide diluted with three or four 
parts of alcohol, and boiling with an upright condenser for 
some time. 



ISOBUTYRIC ACID. 2 29 

C 2 H 5 Br + KCN = C 2 H 5 CN + KBr. 

From ethyl cyanide the propionic acid can be obtained by 
" saponification " with an acid or an alkali. 

2 C 2 H 5 CN + H 2 S6 4 + 4 H 2 = 2C 2 H 5 C0 2 H + (NH 4 ) 2 S0 4 
C 2 H 5 CN + KOH + H 2 = C 2 H 5 C0 2 K + NH 3 . 

These reactions are general in their application. Since 
halogen derivatives of the hydrocarbons are readily prepared 
from primary alcohols, and since the chlorides of acids can 
be reduced to aldehydes and primary alcohols, it is possible 
to start with methyl alcohol and prepare from it, syntheti- 
cally, the whole series of normal fatty acids. 

Normal Butyric Acid, or Butanoic Acid, CH 3 CH 2 CH 2 C0 2 H, is 
found in comparatively small amount in butter in the form 
of its glycerol ester, C 3 H 5 (C 3 H 7 2 ) 3 . Butyric acid is prac- 
tically prepared by the fermentation of glucose, in the pres- 
ence of calcium carbonate, and under the influence of a 
ferment which is found in old Limburger cheese. 



Isobutyric Acid, or Methylpropanoic Acid, 

™ 3 >CH-C0 2 H, 

is obtained by the oxidation of the isobutyl alcohol, iso- 
lated from fusel oil, or by the saponification of isopropyl 
cyanide, which can be prepared from isopropyl iodide, 
CH 3 CHICH 3 . 

The calcium salt of normal butyric acid is less soluble in 
hot than in cold water. A cold, saturated solution of the 
salt gives, therefore, a precipitate on warming. The cold 
saturated solution of calcium isobutyrate, on the contrary, 
gives no such precipitate. 



230 ORGANIC CHEMISTRY. 

Acids, C 5 H 10 O 2 . — Four acids of the formula, C 5 H 10 O 2 , are 
known. The most important is the ordinary valeric acid, or 
more correctly isovaleric acid (methyl-3-butanoic acid), 

3 >CHCH 2 C0 2 H. This is found in valerian root, and 
CH 3 

is also prepared by the oxidation of the isoamyl alcohol of 
fusel oil. (How could it be prepared from isobutyl al- 
cohol ? ) 

Palmitic Acid, C 16 H 32 2 , and Stearic Acid, C 18 H 36 2 , 
are found in the form of their glycerol esters, palmitin^ 
C 3 H 6 (C 16 H 31 2 ) 3 , and stearin, C 3 H 5 (C 18 H 35 2 ) 3 , in many of the 
natural fats. Palmitin is found especially in palm-oil, in 
Japanese vegetable wax, Chinese tallow, and cocoanut-oil. 
Stearin is found in tallow, in shea-butter from West Africa, 
and in many other fats. 

Soaps. — When fats are treated with sodium hydroxide, or 
sodium carbonate, they are saponified, and sodium salts of 
the fatty acids are formed. These sodium salts are the or- 
dinary soaps. 

C 3 H 5 (C 16 H 31 2 ) 3 + 3 NaOH = 3 C 16 H 31 2 Na+C 3 H 5 (OH) 3 . 

Palmitin. Sodium palmitate. Glycerol. 

The sodium and potassium salts of the higher fatty acids 
are easily soluble in water, but the calcium and magnesium 
salts are insoluble. With a " hard " water, therefore, soap 
will not produce a " lather" till enough has been used to pre- 
cipitate all of the calcium and magnesium present. 

The soaps are, apparently, partly decomposed in dilute solu- 
tions with liberation of free alkali, which then attacks grease 
and removes it. Since, however, soaps will aid in the removal 
of paraffin oils which are not attacked by alkali, it seems evi- 
dent that the soap attacks or dissolves oily substances di- 



STRUCTURE OF THE NATURAL FATTY ACIDS. 23 I 

rectly in such a manner that they will subsequently form an 
emulsion with the water, and can then be washed away. 

Structure of the Natural Fatty Acids. — Krafft has proved 
that the natural fatty acids from caprylic acid to arachidic 
acid have the normal structure. By distilling a mixture of 
barium stearate and barium acetate the ketone C 17 H 35 COCH 3 
was obtained. 

(C 17 H 35 C0 2 ) 2 Ba+(C 2 H 3 2 ) 2 Ba-2C 17 H 35 COCH3+2BaC03. 

This ketone, by oxidation, gave margaric acid, C 16 H 33 C0 2 H. 
Stearic acid must therefore have the structure 

C 16 H 33 CH 2 C0 2 H. 

The same process was repeated till capric acid, 

C 9 H 19 C0 2 H, 

was reached. Since capric acid has been prepared from 
normal octyl iodide, 

CH 3 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 I, 

by the acetacetic ester synthesis (p. 350) the normal structure 
of stearic acid and of the intermediate acids is demonstrated. 
By reducing the chloride of stearic acid, C 17 H 35 C0C1, the alde- 
hyde, C 17 H 33 COH, and the alcohol, C 17 H 35 CH 2 OH, and from 
the last the iodide, C 17 H 35 CH 2 I, were prepared. From this, 
by the acetacetic ester synthesis, again, arachidic acid was 
obtained. This must have, therefore, the structure 

C 17 H 35 CH 2 CH 2 C0 2 H, 

and, since stearic acid has been shown to have the normal 
structure by the work described above, the proof is com- 
plete. 



232 ORGANIC CHEMISTRY. 

ACIDS C K H,„_A. 



Melting Boiling 
Point. Point. 



Acrylic acid 


CH 2 = CH — C0 2 H 


8° 


i 4 o° 




Crotonic acid (A^Cisbutenoic acid) 


H — C — CO,H 

II 
H — C — CH S 


7 2° 


i8 5 ° 




Isocrotonic acid (A 1 Transbutenoic acid) 


H - C — CO,H 

II 
CH 3 — C — H 


iS-5°. 


I 7 2° 




Methacrylic acid (Methyl propenoic acid) 


CH 2 ^. 

CHs/ C — C0 2 H 


i6° 


160.5 


Cyclopropane carboxylic acid 


CH 2 

1 > CH — C0 2 H 
CH, 


i 9 ° 


181 - 


184 


Allylacetic acid (A 3 Pentenoic acid) CH 2 = 


CH — CH 2 CH 3 C0 2 H 


fluid 


187 - 


189 


Ethylidene propionic acid (A 2 -Pentenoic acid) 

CH 8 — CH = CH — CH 2 C0 2 H 


fluid 


1930- 


194° 


Propylidene acetic acid (A 1 -Pentenoic acid) 

CH 3 CH 2 — CH = CHC0 2 H 


fluid 


i94°- 


!95° 



Angelic acid CI *| > C = C < ^§» H (?) 45° i8 5 ( 

Tiglicacid CH i > C = C <CH3 H < ?) 6 *-5° J 9»- 

Dimethyl acrylic acid (A 1 Methyl-3-butenoic * acid) 

gg 3 >C = CH — C0 2 H 70 i95 c 



Cyclobutane carboxylic acid | | fluid ig2 c 

— CH 2 



CH 2 — CH — C0 2 H 
CH 2 



Hydrosorbic acid (A 2 Hexenoic acid) 

CH 3 — CH 2 — CH = CH — CH 2 C0 2 H fluid 2 o8 c 

Pyroterebic acid £g 3 > C = CH — CH 2 C0 2 H 6° 2 of 

Dihydro-|3-Campholytic acid (Dihydroisolauronolic acid) 
(2-3,3 Trimethylcyclopentane carboxylic acid) 

CH 3 — CH — CH — CQ 2 H 



CH. 



CH 2 fluid 



CH^ — CH * 

Oleic acid (A 8 Cis (or trans) octadecenoic acid) ' || '' Atioo^w. 

H-C-(CH 2 ) 7 C0 2 H I4 286 

Elai'dic acid (A 8 Trans (or cis) octadecenoic acid) 

CsH 17 — C — H 

II 45° 288= 

H — C — (CH 2 ) 7 C0 2 H 

Very many other acids of this group are known. 

* The apparent inconsistency of this name is due to the fact that, in defining 
double unions the carbon atom adjacent to the carboxyl is numbered 1, while in the 
official nomenclature the end carbon atom is 1. 



ACRYLIC ACID. 233 

Acrylic Acid, CH 2 = CHC0 2 H (propenoic acid), may be 
prepared by treating /3-iodo-propionic * acid, CH 2 ICH 2 C0 2 H, 
with alcoholic potash ; by heating salts of either lactic acid, 
CH 3 CHOHC0 2 H, or hydracrylic acid, CH 2 OH-CH 2 C0 2 H ; 

//° ■ 

by careful oxidation of acrolein, CH 2 = CH — C , with 

silver oxide ; and by oxidation of 2,3-dibrompropanol-i, 

CH 2 BrCHBrCH 2 OH, 
with nitric acid, followed by the reduction of the resulting 
dibrompropionic acid, 

CH 2 BrCHBrC0 2 H, 

with zinc and sulphuric acid. It is to be noticed that re- 
duction in this case merely removes bromine, and does not 
replace it with hydrogen. This sort of action of reducing 
agents upon compounds in which two bromine atoms are 
combined with adjacent carbon atoms is very common. 

The similarity between the first methods given for the 
preparation of acrylic acid and the methods used for the 
preparation of hydrocarbons of the ethylene series is signifi- 
cant. The fact that similar reactions may often be applied 
to compounds of very diverse character is of great practical 
importance in organic chemistry. It should be remembered, 
however, that while the reasoning from analogy based on 
this fact is often an indispensable guide, it is frequently un- 
reliable when used to determine the structure of compounds. 
Often reliable conclusions can be reached only after the accumu- 
lation of a large mass of evidence, and a single line of reason- 
ing, which might seem satisfactory in a text-book, is, at times, 
very delusive in actual work. 

The chemical properties of acrylic acid are largely indi- 

* Derivatives of acids are named by designating the carbon atoms by the Greek 
letters a, /3, y, A, e, £ . . . to, beginning with the carbon atom adjacent to the caiboxyl. 



234 ORGANIC CHEMISTRY. 

cated by its structure. It shows all of the ordinary reactions 
of organic acids, so far as these are not interfered with by 
the presence of the very reactive double union ; and it gives 
the reactions characteristic of unsaturated bodies. It takes 
up two chlorine or bromine atoms directly, giving a-/?-dichlor- 
or a-/?-dibrompropionic acid, CH 2 BrCHBrC0 2 H. It adds 
hydrochloric, hydrobromic, or hydriodic acid, the halogen 
taking the ^-position in accordance with the " positive- 
negative " law (p. 191), giving, for example, /?-iodopropionic 
acid, CH 2 ICH 2 C0 2 H. Nascent hydrogen converts this into 
propionic acid. Fusion with caustic potash gives formic 
acid and acetic acids : 

CH 2 = CHC0 2 H-f2KOH = H-C0 2 K-hCH 3 C0 2 K + H 2 . 

H-C-C0 2 H 
Crotonic Acid (A^isbutenoic acid), || . Ordi- 

H-C-CH 3 

nary crotonic acid is found in croton oil, and is prepared by 
heating a-brombutyric acid, CH 3 CH 2 CHBrC0 2 H, or /?-iodo- 
butyric acid with caustic potash. It is also formed by heat- 
ing paraldehyde with malonic and acetic acids. 

CH 3 -C= H + CH 2 (CO,H _ CH8 _ c ^/C0 2 H +H20 

Aldehyde. Malonic acid. Ethylidene 

malonic acid. 

CH 3 -CH=:C^^ 2 ^=CH 3 -CH = CH-C0 2 H + C0 2 . 

^ C0 2 rl 

The structure of crotonic acid follows from the method 
of preparation, and from the fact that the /?-iodobutyric acid, 
formed by adding hydriodic acid to it, is reduced, by sodium 
amalgam, to normal butyric acid. 

H -C-C0 2 H 
Isocrotonic Acid (A 1 Transbutenoic acid), || 

CH,-C-H 



ISOCROTONIC ACID. 235 

When acetacetic ester is treated with phosphorus penta- 
chloride it is converted into the chlorides of two isomeric 
chlorcrotonic acids. 
CH 3 C(OH) = CH-C0 2 C 2 H 5 + 2 PC1 5 

= CH 8 -CC1 = CH-C0C1 + HC1 + 2P0C1 8 + C 2 H 6 C1, 
or CH 3 CO-CH 2 -C0 2 C 2 H 5 + 2PCl 5 

= 2POCl 3 + C 2 H 5 Cl+CH 3 CCl 2 -CH 2 COCl, 
= CH 3 -CC1=CH-CQC1+HC1. 
On treatment with water, these chlorides are converted 
into two chlorcrotonic acids, one of which melts at 94 , and 
is called /^-chlorcrotonic acid, while the other melts at 59 , 
and is called /?-chlorisocrotonic acid. 
CH 3 -CCl = CH-COCl-fH 2 

= CH 3 -CC1 = CH-C0 2 H + HC1 

^-Chlorcrotonic acid, 
or /3-Chlorisocrotonic acid. 

One of the acids is easily volatile with water vapor, while 
the other is not, and they may be separated by this means. 

The first of these acids gives, by reduction, crotonic acid ; 
the second gives isocrotonic acid. In the earlier discussion 
of the structure of the crotonic acids, it was thought that 
ordinary crotonic acid has the structure CH 3 — CH = CH — 
C0 2 H, and isocrotonic acid that represented by the formula 
CH 2 = CH-CH 2 -C0 2 H. The further development of 
organic chemistry has led, however, to the discovery that 
very many compounds containing a double union exist in 
two forms which are evidently dependent on the mere pres- 
ence of the double union and not on the position of that 
union. This peculiar form of isomerism has been called by 
Michael (Ber. d. chem. Ges. 19, 1384) alloisomerism, and the 
more stable of the two given forms is distinguished by the 
prefix'' alio." In the present case the ordinary crotonic acid 
would be called allocrotonic acid, since isocrotonic acid is 



236 ORGANIC CHEMISTRY. 

converted into it by heating. Michael attempts no explana- 
tion of the cause of this kind of isomerism. 

Stereoisomerism. — On the basis of his conception of the 
arrangement in space (p. 137) of the atoms of carbon com- 
pounds, Van't Hoff has proposed a theory with regard to 
the sort of isomerism under consideration. In single unions 
between carbon atoms it is assumed that each atom is free 
to rotate around the point of union. When, however, a 
double union is formed, this free rotation is supposed to be 
no longer possible. On this supposition the crotonic acids 
may exist in two forms, which will be apparent from the 
following figures 



C0 2 H Htt ^C0 2 H 





H 3 C 



Crotonic acid "Cis "form, plane symmetric Isocrotonic acid " Trans " form, central or 
configuration. axially symmetric configuration. 

The prefixes "cis," meaning "on this side," and "trans," 
meaning " across," have been proposed to distinguish the 
two forms. 

The assignment of the true configuration to the isomers, is 
not always possible. In the present case, ordinary crotonic 
acid is supposed to have the " cis " form because it is pro- 
duced by the reduction of tetrolic acid, CH 3 — C = C — C0 2 H. 
The significance of this will be apparent from the figures of 
the crotonic acids. Only the first form could readily result 
by the addition of hydrogen to tetrolic acid. 

The best evidence that the two crotonic acids are stereo- 



HYDROSORBIC ACID. 237 

meric bodies, and not " place isomers," * lies in the fact that 
each gives with hydriodic acid the same /?-iodobutyric acid, 
CH 3 CHICH 2 C0 2 H. 

Stereoisomers, as a rule, readily pass from one form 
into the other, and bodies containing double unions often 
undergo other rearrangements. For these reasons evidence 
with regard to the relations between such compounds is often 
conflicting, and even more than the usual caution against 
dogmatic conclusions is required. 

Hydrosorbic Acid (A 2 Hexenoic acid), CH 3 CH 2 — CH = 
CH — CH 2 C0 2 H, is prepared by the reduction of sorbic acid, 
CH 3 CH = CH-CH = CH-C0 2 H, with sodium amalgam. 
The apparent shifting of a double union during the re- 
duction has been found to be general for many similar 
cases. Apparently the hydrogen adds itself to the a- and 
8-carbon atoms, while the valences of the /3- and y-carbon 
atoms, momentarily free, result in a union between those 
atoms. (Baeyer, Ann. d. Chem. (Liebig), 251, 279 ; Thiele, 
Ibid, 306, 87 ; Erlenmeyer Jr., Ibid, 316, 43.) 

When hydrosorbic acid is boiled for a moment with 
sulphuric acid which has been diluted with an equal volume 
of water, it is converted into caprolactone. Water is, appar- 
ently, added and split off again thus : — 
CH 3 CH CH=CH-CH CO H-* CH 3 CH CH-CH CHCOH 

6 2 2 2 d 2 222 

OH 
-> CH 3 -CH 2 -CH-CH,-CH 2 -CO 

6 1 

Caprolactone. 

This reaction is characteristic of almost all /?-y-unsatu- 
rated acids. The same transformation is also effected by 
strong hydrobromic acid or, in many cases, by merely boiling 

* That is, isomers in which the positions of the double unions and of the hydrogen 
atoms differ. 



238 ORGANIC CHEMISTRY, 

the acids. (Fittig, Ber. d. chem. Ges. 27, 2667 ; Ann. d. 
Chem. (Liebig), 283, 51.) 

When hydrosorbic acid is boiled with a strong solution of 
sodium hydroxide it is changed to b^hexenoic acid, CH 3 CH 2 - 
CH 2 CH = CHC0 2 H. This transformation is also supposed 
to be due to the addition, and subsequent loss of water, and 
is characteristic of many /?-y-unsaturated acids. (Baeyer, 
Ann. d. Chem. (Liebig), 251, 268 ; Fittig, Ann. d. Chem. 
(Liebig), 283, 50.) 

For the conduct of the halogen addition products of such 
acids, see p. 395. 

Oleic Acid, C 8 H 17 CH = CH(CH 2 ) 7 C0 2 H, is found in the 
form of its glyceride olein in olive-oil, lard and other fats. 
Nitrous acid converts oleic acid into elaidic acid. Since 
hydriodic acid reduces both oleic acid and elaidic acid to 
stearic acid, CH 3 (CH 2 ) 16 C0 2 H, each must contain a normal 
chain of carbon atoms. Since the dibromide of each acid 
gives with alcoholic potash, stearolic acid, C 18 H 32 2 , it seems 
probable that the double union is in the same position in 
each and that the acids are stereomeric. Stearolic acid is 
converted, by oxidation with nitric acid, into stearoxylic acid, 
C 18 H 32 4 , and the latter, by further oxidation, into a mixture 
of pelargonic acid, C 9 H 18 2 , and azelaic acid, (CH 2 ) 7 (C0 2 H) 2 . 
These reactions establish the structure : — 

C H 3 C H 3 C H 3 

(CH 2 ) 7 (CH 2 ) 7 (CH 2 ) 7 

I I I 

C CO C0 2 H 
III I 

C CO C0 2 H 

(CH 2 ) 7 (CH 2 ) 7 (CH 2 ) 7 

C0 2 H C0 2 H C0 2 H 

Stearolic acid. Stearoxylic acid Pelargonic and azelaic acids. 



STEREOISOMERISM OF CYCLIC COMPOUNDS. 239 

By careful oxidation with potassium permanganate, oleic 
acid is converted into dioxystearic acid, 

CH 3 (CH 2 ) 7 CHOHCHOH(CH 2 ) 7 C0 2 H. 

This reaction, again, is characteristic of unsaturated acids. 
(See also pp. 15.3 and 162.) 

By fusion with caustic potash oleic acid gives palmitic 
and acetic acids. An erroneous structure was formerly 
ascribed to the acid on the basis of this fact. 

The properties of the cyclic acids of the formula C n H 2?l _ 2 2 , 
so far as they are peculiar, follow in general from the prop- 
erties of the cyclic hydrocarbons. They are to be con- 
sidered as saturated compounds, and as such resemble the 
saturated fatty acids. A cold solution of an unsaturated 
acid in sodium carbonate gives, with potassium perman- 
ganate, an immediate brown coloration or precipitate. Cyclic 
acids with the same treatment retain for a longer or shorter 
time the red color of the potassium permanganate. This 
means of diagnosis has proved to be of very great service in 
practical work. 

Stereoisomerism of Cyclic Compounds. — When a cyclic 
compound contains two groups or atoms combined with 
different carbon atoms a " cis " and " trans " stereoisom- 
erism is possible. Thus, hexahydroorthotohiic acid (1 methyl 

C H 2 — C H 2 — CH — C H 3 
cyclohexane-2-carboxylic acid), \ \ , ex- 

CH 2 -CH 2 -CH-C0 2 H 
ists in two forms. In one of these ("cis") the methyl and 
carboxyl are supposed to be on the same side of the plane of 
the ring ; in the other form (" trans " or "cis trans ") they 
are supposed to be on opposite sides of that plane. The 
relation is most clearly apparent by use of a model. Iso- 
merism of this kind has been observed in very many cases. 



240 ORGANIC CHEMISTRY. 

ACIDS, C n H ln _ 4 2 . 

Melting Boiling 
Point. Point. 

<£S"d) CH=C-C0 2 H 

Tetrolicacid CH 3 — C=C— C0 2 H 76° 203 

CH 3 — CH=CH— CH=CH— C0 2 H 134=5° 228° 



Sorbic acid 

(A 1 ' 3 Hexenoic acid) 



A 1 -Tetrahydrobenzoic acid , , 

(A^Cyclohexenoic acid J,tt prr JJtt 

CH,— C=C— C0 2 H 
/3-Campholytic acid 
(Isolauronolic acid) 
A 1 -2,33 Trimethyl cyclo- ( 



CH 2 — CH 2 — C— C0 2 H 

I || 29° 2 4 o°-2 4 3 c 



CH 2 133° 256° 



pentenoic acid Ch'^ — CH 2 

Many other acids of this general formula are known. 
Four classes of acids having the formula C„H 2w _ 4 2 are 
possible. 

1. Acids having one triple union (or acetylene union). 

2. Acids having two double unions (or ethylene unions). 

3. Cyclic acids having one double union. 

4. Bicyclic acids. 

Acids of each class except the last are represented in the 
table. Tetrolic acid (p. 236) and sorbic acid (p. 237) have al- 
ready been referred to. The other acids of the group do not 
require especial mention. 

The principles which underlie the formation of acids in 
groups which contain still less hydrogen are sufficiently ap- 
parent from those which have been considered. Of these 
groups, that containing the " aromatic " acids is of greatest 
importance. 

Aromatic Acids, C„H 2n _ s O. 







Melting 


Boiling 






Point. 


Point. 


Benzoic acid 


C 6 H B C0 2 H 


121.4° 


249° 


o-Toluic " (1.2) 


(^ tt /C0 2 H 

L(iH4 \CH 3 


102° 


259° 


m- " " (1.3) 


" 


II0.5° 


263° 


P- " " (1.4) 


C( 


180 


274° 





BENZOIC ACID. 




241 


a-Toluic acid 
Phenyl acetic acid 


C H 5 CH 2 CO 2 H 


76.5° 


265.5° 


Hemellithic acid 


/CH 3 i 

QH3-CH3 2 

\C0 2 H 3 




144° 





Paraxylic acid 


/CH 3 1 

» C 6 H 6 -CH 3 2 

\C0 2 H 4 




163 





Neighboring xylic acid 


/CH 3 1 

C G H 3 — CO,H 2 

\CH 3 3 




116 


274-5° 


Xylic acid 


/CH 3 1 

Q;H 3 — CH 3 3 

\CQ 2 H 4 




1 26 


267° 


Mesitylenic acid 


/CH 3 1 

C 6 H 3 -CH 3 3 

\C0 2 H 5 




166 





Isoxylic acid 


/CH 3 1 

C H 3 — CO,H 2 

\CH 3 4 




132 


268 


Hydrocinnamic acid 


C H r ,CH 2 CH 2 CO 2 H 


48.7° 


279.8 


Cuminic acid 


r „ /COoH 1. 
\CH(Cg3 4- 


116 





Cinnamic acid 


C G H n CH=CH- 


-C0 2 H 


133° 


300 



Very many other acids of this group and of groups con- 
taining less hydrogen are known, but only a few of these 
need be mentioned. 

Benzoic Acid, C 6 H 5 C0 2 H, was originally obtained from 
gum benzoin by sublimation, or by treatment with alkalies. 
It is also prepared : 

1. By the oxidation of benzyl alcohol, C g H 5 CH 2 OH, ben- 
zaldehyde, C 6 H 5 CHO, toluene, C 6 H 5 CH 3 , benzyl chloride, 
C 6 H 5 CH 2 C1, ethyl benzene, C 6 H 5 C 2 H 5 , or practically of any 
derivative of benzene containing but a single side chain and 
in which the atom attached to the nucleus is carbon. 

2. By the saponification of phenyl cyanide. 

2 C 6 H 5 CN + H 2 S0 4 -f- 4 H 2 = 2 C 6 H 5 C0 2 H + (NH 4 ) 2 S0 4 . 

The phenyl cyanide is prepared : 

a. By distilling a mixture of potassium cyanide with chlor- 
benzene, C 6 H 5 C1, brombenzene, C 6 H 5 Br, or potassium ben- 
zene sulphonate, C 6 H 5 S0 3 K. 



242 ORGANIC CHEMISTRY. 

b. By the action of cuprous cyanide on benzene diazonium 
chloride (p. 461) : 

2 C 6 H 5 N = N + Cu 2 C 2 N 2 - 2C 6 H 5 CN + 2 N 2 + Cu 2 Cl 2 . 

I 
CI 

3. By heating benzotrichloride, C 6 H 5 CC1 3 , with water or 
alkalies. 

4. By the action of carbon dioxide and aluminium chloride 
on benzene. 

5. By the decomposition of hippuric acid by hydrochloric 
acid : 

C 6 H 6 C - NHCH 2 C0 2 H + HC1 +H 2 

= C 6 H 5 C0 2 H + CH 2 (^J C | 

Chloride of glycocoll 
or aminoacetic acid. 

Benzoic acid crystallizes in needles. It is difficultly solu- 
ble in cold water, more easily soluble in hot water, very 
readily soluble in alcohol and ether. It sublimes easily, and 
is quite readily volatile with steam. The vapors produce 
coughing. 

Oxidation of Derivatives of Benzene. — The oxidation of 
derivatives of benzene not only furnishes a means of prepar- 
ing many acids of the aromatic series, but it also serves as a 
means of determining the structure of many compounds. 
Thus, if the oxidation of a compound gives benzoic acid, it 
is evident that the original compound had but one side chain. 

If the oxidation yields a phthalic acid, C 6 H 4 m 2 , not 

only must the compound oxidized have had 'two side chains, 
but, according as phthalic acid (ortho), isophthalic acid 
(meta) or terephthalic acid is obtained, must the position 
of the original groups have been ortho, meta, or para. 



OXIDATION OF AROMATIC COMPOUNDS. 



243 



The most common oxidizing agents are chromic acid, di- 
lute nitric acid, potassium permanganate, and potassium fer- 
ricyanide. 

Chromic Acid (or, * usually, potassium pyrochromate and 
sulphuric acid) oxidizes readily side chains which have no 
other group in the ortho position. Thus, cymene, 

rH /CH 3 

Wt 1 * / CHo 



or paraxylene, 



C 6 H 4 



/CH 3 
\CH, 



are readily oxidized to terephthalic acid, 

/C0 2 H 1 

\ C0 2 H 4' 

by chromic acid, but nitroparaxylene, 

CH, 



C 6 H 4 



NO, 



gives only nitrotoluic acid, 



ch, 



CH 3 



with the same agent. 



CO,H 



N0 2 



Nitric Acid acts very much as chromic acid does, but less 
vigorously, so that intermediate oxidation products are more 



244 ORGANIC CHEMISTRY. 

easily obtained by means of it than by means of chromic 
acid. Thus, cymene gives with nitric acid paratoluic acid, 

C 6 H 4 ^r^\ T • The presence of an ortho group interferes 
x C(J 2 ri 

with oxidation by nitric acid, as in the case of chromic acid, 
but there are a few cases where such groups have been oxi- 
dized by this agent. 

Potassium Permanganate is used in alkaline solutions. 
Ortho groups may be oxidized by it, and no selective action 
has been established. 

Potassium Ferricyanide is also used in alkaline solutions. 
In nitro compounds, a methyl group in the ortho or para 
position is much more easily oxidized than one in the meta 
position. Thus, nitroparaxylene gives the nitrotoluic acid, 

CO,H 



NO, 



CH 3 

with this agent. 

Cinnamic Acid, C 6 H 5 CH = CH — C0 2 H, is found in liquid 
storax and in a number of other natural products. It is 
prepared : 

i. By heating together benzaldehyde, sodium acetate and 
acetic anhydride (Perkin's synthesis) : 

C 6 H 5 - C - H + CH 3 C0 2 Na + (C 2 H 3 0) 2 

= C 6 H 5 CH = CH - C0 2 Na + 2 C 2 H 4 2 

This reaction, which is both historically and practically a 
very important one, was made the subject of careful investi- 



CINNAMIC ACID. 245 

gation by a number of different chemists, and the following 
facts about it were gradually established. 

a. The condensation is with the sodium salt and not with 
the acetic anhydride. 

b. The condensation occurs with the carbon atom adja- 
cent to the carboxyl in the case of homologues of acetic 
acid. Sodium propionate, CH 3 CH 2 C0 2 H, gives a-methyl 
cinnamic acid, 

C 6 H 5 CH = C - C0 2 H, 



and not phenyl crotonic acid, 

C 6 H 5 H = CH - CH 2 COC 2 H. 

c. The condensation is at first an addition, giving a 

hydroxy acid, followed by a loss of water. This is proved 

by the fact that when the carbon atom adjacent to the 

carboxyl bears but one hydrogen atom, the hydroxy acid 

formed may be isolated. Thus, with sodium isobutyrate, 

CH 

3 > CHC0 9 Na, and isobutyric anhydride, oxypivalinic 
CH 3 

acid, (a-a-dimethyl-/3-phenyl-/3-hydroxy-propionic acid), 

CH 3 

I 
C 6 H 5 -CH - C-C0 2 H, 

I I 

OH CH 3 
is obtained. 

The condensation is closely analogous to the aldol con- 
densation. 

2. By heating benzal chloride with sodium acetate : 

C 6 H 5 CHC1 2 + CH 3 CO s Na = C 6 H 5 CH = CH - C0 2 H 

+ NaCl + HCl. 



This method is of commercial importance. 



246 ORGANIC CHEMISTRY. 

3. By condensation of benzaldehyde with acetone to ben- 
zalacetone, C 6 H 5 CH = CH-COCH 3 (p. 190), followed by 
oxidation to cinnamic acid and chloroform, CHC1 3 , by means 
of sodium hypochlorite (p. 199). 

In addition to the ordinary cinnamic acid, two other forms, 
known as " allo-cinnamic acid" and " isocinnamic acid," are 
known. Theory leads us to expect two stereomeric forms, 



QH 5 - 


-C- 

II 


-H 


and 


H- 


-C- 


5 


H- 


-c- 


-C0 2 H 




H- 


-C- 


-C0 2 H 



but the nature of the third form has not been satisfactorily 
explained.* 

Cinnamic acid and allocinnamic acid give different dibro- 
mides, C 6 H 5 CHBrCHBrC0 2 H, the first melting at 201 , the 
second at 9i°-93°. This can be explained as follows, if we 
consider the order of the atoms and groups in the formulae 
as representing the order of the groups around the carbon 
atoms : 

Br 

I 
C 6 H 5 — C — H C 6 H 5 — C — H , 

II gives I 

H-C-C0 2 H H-C-C0 2 H 

I 
Br 

Br 



H-C-C 6 H 5 H -C-C 6 H 5 

II gives I 

H-C-CCLH H-C-CCLH 



Br 

A consideration of these formulae reveals the fact that 
rotations around the line joining the two carbon atoms can- 

* A very recent paper by Liebermann (Ber. d. chem. Ges., 36, 176), throws doubt 
on the existence of isocinnamic acid. 



PHENYL PROP 10 LIC ACID. 247 

not bring the two dibromides into positions which are 
identical. Thus, rotation of the upper carbon atom in the 
first dibromide till the hydrogen atoms are over each other 
will leave a bromine atom over the carboxyl, and the phenyl 
group over the other bromine atom, relations which are 
different from those of the second dibromide. This can be 
most easily seen by the use of models. It is evident from 
this that when two adjacent carbon atoms each bear three 
different groups, the order of those groups may be the cause 
of isomerism. Isomers of this kind often exhibit differences 
in chemical as well as in physical properties. 

Phenyl Propiolic Acid, C 6 H 5 C = C — C0 2 H, is prepared by 
treating the ethyl ester of cinnamic dibromide with alcoholic 
potash. 

C 6 H 6 CHBrCHBrC0 2 C 2 H 5 + 3KOH = C 6 H 5 C = C - C0 2 K 

+ 2KBr + 2 H 2 + C 2 H B OH 

Phenyl propiolic acid decomposes, on heating with 
water to 120 , into carbon dioxide and phenyl acetylene, 
C 6 H 5 =CH. It is to be noticed that the grouping, — C = C — 
C0 2 H, found in phenyl propiolic acid, produces an instability 
similar to that caused by the grouping — CO — CH 2 C0 2 H 
(p. 351), though perhaps somewhat less in degree. 

Phenyl propiolic acid is also of interest because of the 
ready conversion of orthonitrophenylpropiolic acid into in- 
digo by merely heating it with grape sugar and caustic soda. 

C = C-C0 2 H , TT 

2C 6 H 4 < - +4 H = 



CO CO 

NH > L_C< NH 

Indigo. 



C 6 H 4 <, T - LJ > C = C <^ txj >C 6 H 4 +2 C0 2 + 2 H 2 0. 



248 



ORGANIC CHEMISTRY. 





Bibasic Acids. 


Melting Point. 




C0 2 H, 




Oxalic acid 


1 

C0 2 H 


101.5 


Malonic acid 


rX r /CO,H 

^ W2 \co;h 

CH 2 — C0 2 H 


i33° 


Succinic acid 


CH 2 — C0 2 H 


185° 


Isosuccinic acid 


LH ^ lH \C0 2 H 


130° 


Glutaric acid 


rH /CH,— CO,H 
^^NCHj— C0 2 H 


97-5° 


Pyrotartaric acid 


CH 3 — CH— CO,H 
1 


T T->0 


(Methyl succinic acid) 


CH 2 — CO a H 
CH 2 — CH,— CO,H 


1 12 


Adipic acid 


1 
CH 2 — CH 2 — C0 2 H 


149° 


Symmetric dimethyl- 


CH 3 -CH— C0 2 H 




succinic acid 


1 


195° 


(Fumaroid form) 


CH 3 — CH— C0 2 H 




The same 


{ , 


. , .0 


(Maleinoid form) 




124" 


Pimelic acid 


co /CHo — CH,C0 2 H 
Ubl2 \CH 2 — CH 2 CG 2 H 
CH 3 — CH— C0 2 H 


105° 


Trimethylsuccinic acid 


£g 3 >C-CO,H 


i S 2° 



Suberic acid 
(Ger. Korksaure) 

Azelaic acid 
Sebacic acid 

Fumaric acid 

Malei'c acid 

Mesaconic acid 

Citraconic acid 

Itaconic acid 
Glutaconic acid 



/prr \ / C O, H 

(CH2)li \C0 2 H 

/pTT \ /CO,H 

^ il 2>7\C0 2 H 

/fu \ / CU 2 rl 

(IH2 Kco 2 h 

C0 2 H— CH 

ll 
HC— C0 2 H 

H— C— C0 2 H 

H— C— C0 2 H 
C0 2 H— C— CH 3 

H— C— C0 2 H 
CH 3 -C— C0 2 H 

HC - C0 2 H 
CH 2 =C— C0 2 H 

CH 2 — C0 2 H 



CH- 

CH, 



:CH--CO,H 
,CH 2 — C0 2 H 



140- 
106 



Sublimes at 200° 



8o° 

161° 
132° 



Cyclopropane 1.1 dicarboxylic ^> C. rc?tt 

acid CH 2 NLU2il 



OXALIC ACID. 



249 



Cyclopropane 1.2 dicarboxy- /CH — C0 2 H 



lie acid 
(Cis form) 
The same 
(Trans form) 



The same 
(Trans form) 



Camphoric acid 
(Cis form, active) 



Isocamphoric acid 
(Trans form, active) 



CH 2 I 

\CH— C0 2 H 



CH,— CH— CQ 2 H 



Hexahydroisophthalic acid Att \yr 

(Cis form) 



I I 

CH 2 — CH— C0 2 H 



Melting Point. 
139'' 

175° 
163° 



CH 3 CH 3 

\ / 

c- — c 

/ \ I \ 

CH 3 CH 2 C0 2 H 

CQ 2 H— CH— CH 2 



187" 



Phthalic acid 
Isophthalic acid 
Terephthalic acid 



r H /C0 2 H 
^6«4 NCO ,H 
^ tt /CO,H 

" ctll \C0 2 H 
r H /CO..H 

^6"4\CO,H 



r8 4 

Above 3oo c 
Sublimes 



The acids of this table have been selected chiefly for 
the purpose of illustrating the fundamental forms and the 
possibilities of isomerism. 
C0 2 H 

Oxalic Acid, | -f- 2 H 9 0, is comparatively stable toward 

C0 2 H 
oxidizing agents, and so is frequently formed by the oxida- 
tion of carbon compounds. Especially, it may be prepared 
readily by the oxidation of cane-sugar with nitric acid. It is 
prepared, technically, by heating sawdust with a mixture of 
caustic potash and caustic soda, the oxalic acid being formed 
from the cellulose. 

Oxalic acid is also formed from an aqueous solution of 
cyanogen on standing. 



250 ORGANIC CHEMISTRY. 



CN 


C0 2 NH 4 


1 + 4 H 2 = 


1 


CN 


C0 2 NH 4 



Oxalic acid crystallizes with two molecules of water. It 
is quite possible that the crystallized acid has the structure, 
C(OH) 3 

| , since the presence of strongly negative atoms or 

C(OH) 3 

groups increases the stability of compounds having two or 
more hydroxyl groups combined with one carbon atom. 

Oxalic acid is a " strong " acid, the strongest indeed of 
the organic acids, as shown by the conductivity which gives 
K = about io. 

By careful heating, oxalic acid can be partly sublimed. If 
heated to a higher temperature, it is decomposed partly 
into formic acid and carbon dioxide, chiefly into carbon di- 
oxide, carbon monoxide and water. The latter products are 
also formed when it is heated with concentrated sulphuric 
acid. 

Toward nitric acid oxalic acid is comparatively stable. 
Potassium permanganate, or manganese dioxide, oxidizes it 
quantitatively to carbon dioxide in a warm acid solution. 
On this account either crystallized oxalic acid or ammonium 
oxalate, (NH 4 ) 2 C 2 4 -f H 2 0, can be used in standardizing 
permanganate solutions, or in determining the value of com- 
mercial manganese dioxide for the generation of chlorine. 

Oxalic acid forms neutral and acid salts, and also salts in 
which but one atom of hydrogen in two molecules of the 
acid is replaced. Potassium " tetroxalate," KHC 2 4 .H 2 C 2 4 
-f H 2 0, which belongs to the last class, is sometimes used as 
a standard in preparing normal alkali solutions. 

The oxalates of the metals other than the alkali metals are 
mostly insoluble or difficultly soluble. Many of the metals, 



MALOmC ACID. 251 

however, form double oxalates with potassium, sodium, or 
ammonium, and these are often easily soluble. 

Potassium ferrous oxalate, K 2 Fe(C 2 4 ) 2 + H 2 0, is a pow- 
erful reducing agent, and is used as a developer in pho- 
tography. 

CO IT 

Malonic Acid, CH 2 < 2 , is prepared from chloracetic 

.j C0 2 H 

CH 2 <^ + KCN = CH 2 <^ Na + KCl. 

Sodium salt of cyanacetic acid. 

CH 2 <^ Na +KOH+ H 2 = CH 2 <^J a +NH, 



Malonic acid crystallizes in triclinic plates. It melts at 
i33°-i34°. When heated to i4o°-i5o° it decomposes quan- 
titatively into carbon dioxide and acetic acid. 

CO "FT 
CH ' 2< C0 2 H = CH 3- C ° 2 H + C0 2 . 

All derivatives of malonic acid having two carboxyl groups 
combined with the same carbon atom decompose in a simi- 
lar manner at some temperature below 200 . The combina- 
tion of two carboxyl groups with a single carbon atom causes 
instability, very much as the combination of two hydroxyl 
groups with a single carbon atom does, but the temperature 
of decomposition is higher. It is noticeable that the grouping 
R — CO — CH 2 — C0 2 H is still more unstable (p. 351). 
V If the solution of potassium cyanacetate and potassium 
chloride, obtained by the first reaction above, is evaporated 
nearly to dryness, and the residue heated with a mixture of 
sulphuric acid and alcohol, the diethyl ester of malonic acid is 
formed. * 



The malonic ester prepared in this way contains, also, some cyanacetic ester, 

ch 2 ; 



/C0 2 C 2 H 5 



; \CN 



252 ORGANIC CHEMISTRY. 

2CH 2 <^ 2N V2H 2 S0 4 + 4 C 2 H 5 0^ 

+ Na 2 S0 4 -h(NH 4 ) 2 S0 4 . 
Malonic ester can be distilled without decomposition, 
though its boiling point is 198. 

Condensations with Malonic Ester. — This ester has a very 
unusual interest because of its use for syntheses. When 
it is added to an alcoholic solution of sodium ethylate, 
C 2 H 5 ONa, a sodium salt is formed. To this salt the formula 

CO C TT 

CHNa < 2 2 5 is often assigned. It seems more proba- 

C0 2 C 2 rl 5 

/ OC 2 H 5 

ble, however, that it has the formula CH . When 

^ L(J 2 L 2 H 5 

an alkyl halide or halogen derivative of some carbon com- 
pound is added to this sodium salt, a derivative of malonic 
ester is formed. Thus, 

/ OC 2 H 5 / OC 2 H 5 



CQ 2 C 2 H 4 



Diethyl ester of ethyl 
malonic acid. 



By saponifying this compound, ethyl malonic acid, 

(~T) T-T 
C 2 H 5 CH 2 < 0/ ^. 2 , is formed, and this gives, on heating (see 
CU 2 rl 

above), normal butyric acid, C 2 H 5 CH 2 C0 2 H. 

This method of synthesis is closely related to that in 
which acetacetic ester is used (p. 350), and has proved use- 
ful for the preparation of a great variety of compounds. In 

some cases cyanacetic ester, CH 2 < 2 5 , can be em- 



CONDENSATIONS WITH MALONIC ESTER. 253 

ployed with advantage in place of malonic ester. (See 
below.) 

The second hydrogen atom of the CH 2 group in malonic 
ester or cyanacetic* ester may be replaced by an alkyl group 
in the same manner as the first. ^ 

Malonic ester also adds itself to A 1 unsaturated acids, in 
the presence of sodium ethylate, forming condensation prod- 
ucts in which the malonic ester group attaches itself to the 
/3-carbon atom. * Occasionally halogeji derivatives which 
are easily decomposed give the product derived from the 
unsaturated acia^as well as the normal product. Thus, 
the normal condensation product of malonic ester, sodium 

ethylate, and a-bromisobutyric ester, 3 > CBrC0 2 C 2 H 5 , 

CH 3 

PTT 

is ~*> C — C0 2 C 2 H 5 , and this would give, by saponifica- 
CH 3 

I /C0 2 C 2 H 5 

• \ C0 2 C 2 H 5 
tion and splitting off of carbon dioxide, dimethyl succinic 

PTT 

acid, r;„ 8 >c-co 2 H. 

LH 3 1 

CH 2 C0 2 H 
In addition to this, however, a considerable portion of the 
bromisobutyric ester first loses hydrobromic acid and the 

resulting ester, 2 C — C0 2 C 2 H 5 , then adds malonic ester 



CH,/ 



r<TT PIT ^ ^^2^2^5 



giving the compound, v.w 2 v. 2 n 5 ^ an( j ^^ ^y 



CH 3 CH-C0 2 C 2 H 5 



saponification and loss of carbon dioxide, gives a-methyl- 

glutaric acid, CH 3 — CH< 2 2 2 . In this case 

CU 2 rl 

cyanacetic ester gives almost exclusively the normal product, 



254 ORGANIC CHEMISTRY. 

and hence is much more suitable for the synthesis when 
dimethyl succinic acid is desired. (Bone and Sprankling, 
/. Chew,. Soc. (London), 75, 845.) 

CH 2 -C0 2 H 
Succinic Acid, | , is found in amber, as is indi- 

CH 2 -C0 2 H 

cated by its name. It can be prepared, synthetically, from 
ethylene bromide, CH 2 BrCH 2 Br, by converting this into 

CH 2 -CN 
ethylene cyanide, | , and saponifying the latter. 

CH 2 -CN 

Another synthetic method consists in condensing malonic 
ester with chloracetic ester, C1CH 2 — C0 2 C 2 H 5 , by the methods 
just given. This gives the series : — 

C0 2 C 2 H 5 C0 2 C 2 H 5 C0 2 H 

CH 2 -»CH-CH 2 C0 2 C 2 H r ->CH-CH,-CO.,H->CH.,CH 2 -C0 2 H 
I I I " " I 

C0 2 C 2 H 5 C0 2 C 2 H 5 C0 2 H CO.,H 

Ethenyl tri- 
carboxylic acid. 

Succinic acid can also be prepared by reducing tartaric 
acid with hydriodic acid (p. 332). 

If succinic acid is heated some what. above 200 , or if it is 
treated with phosphorus pentachloride, phosphorus oxychlo- 
ride, acetyl chloride, or other dehydrating agents, it gives an 
" inner " anhydride, which evidently contains a ring of four 
carbon atoms and one oxygen atom, 

CH 2 -C0 2 H CH 2 -CO\ 

2 I +POCI3 = 2 I O + HPO3 + 3HCI 

CH 2 -C0 2 H CH 2 -CO/ 

All of the derivatives of succinic acid with an open chain 
form similar anhydrides on merely heating to about 200 
(Auwers, Ann. d. Chem. 285, 223). Orthophthalic acid, 



GLUTARIC ACID, 255 

C0 2 H H-C-C0 2 H 

C 6 H 4 < ro 2 TT, maleic acid, || , and its deriva- 

2 H-C-C0 2 H 

tives, the " cis " forms of the 1,2 dicarboxylic acids of 

/ • /CH-C0 2 H\ , , , , 

cyclopropane CH 2 . 1 and cyclobutane, and 

V x CH-C0 2 H/ 

both " cis " and " trans " forms of the similar acids of cy.clo- 

pentane and cyclohexane, form similar inner anhydrides. 

C0 2 H-C-H 

Fumaric acid, || , and the " trans " forms of 

H-C-C0 2 H 

the 1,2-dicarboxylic acids of cyclopropane and cyclobutane, 

form no similar anhydrides. These facts are significant in 

their relation to the structure of these acids. 

Succinic anhydride gives, with sodium ethylate, sodium 

CH 2 — C0 2 C 2 H 5 

ethyl succinate, | 

CH 2 -C0 2 Na 

CO TT 
Isosuccinic Acid (methyl malonic acid), CH 3 — CH< 2 , 

may be prepared by the malonic ester synthesis from malonic 
acid, or from a-brompropionic acid, CH 3 CHBrC0 2 H, by the 
same methods used for the preparation of malonic acid.* 

Isosuccinic acid decomposes, on heating, into propionic 
acid and carbon dioxide. 

pir CO TT 

Glutaric Acid, CH 2 < 2 2 , can be prepared from 

CH 2 — CU 2 rl 

trimethylene bromide (1,3 dibrompropane), CH 2 BrCH 2 CH 2 Br, 
through the cyanide. Also by the condensation of formal- 
dehyde with malonic ester, under the influence of a little 
diethylamine, followed by the saponification of the resulting 
dicarboxylglutaric ester, and decomposition of the tetra- 

* The student will do well to write the reactions implied in these statements. 



256 ORGANIC CHEMISTRY. 

basic acid which is formed. (Knoevenagel, Ber. d. chem. 

Ges. 27, 2346.) 

„.__ C0 9 C 9 EL 
CH< 



CK 



- I - 
HI 



C0 2 C 2 H 



CH 2 C0 2 H 



O I -> CH 2 < 

E 
I 



H l 2 "CH 2 C0 2 H 



rT T .C0 2 C 2 H 5 
< C0 2 C 2 H 5 

PIT CO 

Glutaric acid yields an anhydride, CH 2 < 2 rr) > O, 

on warming with acetyl chloride, but forms one only slowly 
when heated to 290 . The " cis " forms of the 1,3 cyclobu- 
tane, cyclopentane, and cyclohexane dicarboxylic acids pro- 
duce anhydrides, while the "trans" forms of the same acids 
do not. 

CH 2 -CH 2 -C0 2 H 
Adipic Acid, | , is formed, along with 

CH 2 — CH 2 — C0 2 H 
other acids, by the oxidation of natural fats. It is best 
prepared by the oxidation of the cyclohexane of Russian 
or Californian petroleum with strong nitric acid. It is also 
formed by the electrolysis of the potassium salt of the acid 

CH 2 -C0 2 C 2 H 5 
ester of succinic acid, | . Two of the ions, 

CH 2 -C0 2 K 
CH 2 -C0 2 C 2 H 5 

, liberated by the electrolysis, decompose with 
CH 2 -C0 2 . 
loss of carbon dioxide, and the residues combine to form 

CH 2 — CH 2 — C0 2 C 2 H 5 
adipic ester, | . (Brown and Walker, Ann. 

CH 2 -CH 2 -C0 2 C 2 H 5 

Chem, (Liebig) 261, 117.) 



MALEIC ACID. 257 

Adipic acid forms no inner anhydride. It melts at 149 , 
and boils without decomposition at 265 , under a pressure of 
100 mm. 

When calcium adipate is distilled, cyclopentanone is 
formed (p. 192). ' 

^. ,. . ., -r-i-r-r CH 9 CH, C0 9 H . .. 

Pimehc Acid, CH 2< CH _ CH _ CQ H > is most easily 

prepared by the reduction of salicylic acid by means of 
alcohol and sodium. 

CH = CH-C-C0 2 H CH 2 -CH 2 -CH 2 C(XH 

I || +4 H + H 2 0= I 

CH = CH-C-OH CH 2 -CH 2 -C0 2 H 

Pimelic acid forms no inner anhydride, but the distillation 
of its calcium salt gives cyclohexanone (p. 192). 

C0 2 H-C-H 
Fumaric Acid, || , is formed by heating 

H-C-C0 2 H 
CHOH-C0 2 H 
malic acid, | , or bromsuccinic acid, 

CH 2 -COoH 
CHBr-C0 2 H 

. It is difficultly soluble in water. When 
CH 2 -C0 2 H 

heated to 200 , it sublimes without melting. When heated 
to a higher temperature it partly decomposes, and is partly 
converted into maleic anhydride. It is also converted into 
maleic anhydride by warming to ioo° with acetyl chloride 
and acetic acid, 

CH-C0 2 H 
Maleic Acid, || . The anhydride of maleic acid, 

CH-C0 2 H 
CH- CO 

> O, is formed by distilling malic acid, fu- 
CH - CO 
marie acid, or by heating monobromsuccinic anhydride, 



258 ORGANIC CHEMISTRY. 

CH 2 -CO 

> O. Maleic acid melts at 130 , and is very 
CHBr-CO 

easily soluble in water. By heating in a vacuum at ioo°, it 
is readily converted into its anhydride. 

Fumaric and maleic acid are supposed to represent a 
" cis " and " trans " stereoisomerism similar to that of the 
crotonic acids. The " cis " formula is given to maleic acid 
because of the ease with which it forms an anhydride. 

Fumaric and maleic acid give, with bromine, two isomeric 
CHBr-C0 2 H 
bibromsuccinic acids, | . Their relation to each 

CHBr-C0 2 H 
other is, apparently, similar to the relation between the two 
cinnamic acid dibromides (p. 246). 

Mesaconic, Citraconic, Itaconic, and Glutaconic Acids are 

isomeric acids, whose relationships are apparent from the 
formulae given in the table. 

Hexahydroisophthalic Acid, 

CH 2 -CH-C0 2 H 
I I 

CH 2 CH 2 , 

I I 

CH 2 -CH-C0 2 H 

has been referred to (p. 100) because of the interest which 

attaches to it in establishing the formula for benzene. It 

exists in both the '' cis " and " trans " form. Only the " cis " 

form gives an anhydride. 

Camphoric Acid, C0 2 H 

I 
CH 3 — C — v-^H 2 

•I 
CH 2 

^ 3 >C-CH-C0 2 H 



CAMPHORIC ACID. 



259 



/ C0 

is prepared by the oxidation of camphor, C 8 H 14 | , by 



\ 



CH< 



means of nitric acid. It is of interest because it is chiefly 
through a study of camphoric acid that the structure of 
camphor has been established. Only an outline of the more 
important steps in the establishment of the formula can be 
given. When camphoric acid is further oxidized it gives 
a tribasic acid, camphoronic acid, C 6 H n (C0 2 H) 3 . Cam- 
phoronic acid gives, when heated, trimethyl succinic acid, 
CH, 



CH 3 



>C-C0 2 H 

I 



CH 3 -CH-C0 2 H 

This led Bredt, in 1893, to propose the formula, 



CH 3 

CH 3 
CH, 



CH 2 -C0 2 H 
I 



-C 

I 

>c 



C0 2 H 



C0 2 H 



for camphoronic acid, and the formula 
CH S 



CH 3 
CH, 



>C — C- 



co 



CH- 

J 



CH 2 

-CH, 



or 




CH 9 



: — CH 2 CH 2 CH- 

for camphor. 

Perkin prepared camphoronic acid synthetically a few 
years later, and so demonstrated the truth of Bredt's formula 
for that acid. Since camphoric acid is, in all of its proper- 
ties, a saturated compound, it must contain a ring of carbon 
atoms, and the only possible grouping consistent with the 
formula of camphoronic acid must contain the skeleton 



26o 



ORGANIC CHEMISTRY. 



CH 3 
CH„ 



>G 5 - 1 C 



/CH 3 
\C0 9 H 



*^4 3^ 

The only question remaining was as to whether the second 
carboxyl group is combined with the carbon atom numbered 
2, 3, or 4. The evidence upon this last point is not all of 
it consistent, but at present is almost conclusively in favor 



of the formula, CH< 



>C 



/CH 3 
\C0 9 H 



CH, 



CH- 

I 
C0 9 H 



CH ; 



The most important facts favoring this structure are . 

1. Isocamphoric acid forms no anhydride, thus resembling 
hexahydroisophthalic acid, and not hexahydrophthalic acid. 

/C0 2 H 

2. Camphanic acid, C 8 H 13 — CO , gives by simple reac- 

tion a ketonic acid, C 8 H 13 . 2 , which evidently contains 

oxygen in place of the carboxyl and hydrogen atoms which are 
attached to the carbon atom 4 above, since the acid is stable, 
while if the oxygen were in position 2 the acid would be un- 
stable. This excludes position 2 for the second carboxyl. 

3. 2 ,33-trimethylcyclopentanone, 



CH„ — CH 



CH ? 
CH, 



>C- 



CO 

I 
CH, 

I 
-CH, 



PHTHALIC ACID. 26 1 

has been prepared synthetically, and also from /3-campholytic 
acid by a series of reactions which demonstrate that the 
acid has the structure, 

CH 3 - C =C-C0 2 H 
I 
CH 2 . 

chI> c -^ 

a-Campholytic acid, C 8 H 13 C0 2 H, retains the secondary car- 
boxyl of camphoric acid, and can be converted easily to 
/3-campholytic acid by warming with dilute acids. But when 
a-campholytic is reduced to the acid, C 8 H 15 C0 2 H, and the 
carboxyl and a hydrogen atom of the latter are replaced 
by oxygen, the resulting cyclic ketone is different from 
the 2,33-trimethylcyclopentanone. The structure of the 
a-campholytic acid, which is nearest to that of camphor, 
must be different, therefore, from that of the /3-campholytic 
acid, and is, undoubtedly, 
CH 3 



>C-CH-C0 2 H 



CH 2 
I 
CH 3 -C = CH 

the transformation of it into /3-campholytic acid involving a 
transfer of a methyl group from one carbon atom to another. 
Such a structure is probable only in case the second carboxyl 
group of camphoric acid occupies position 4. 

Phthalic Acid, C 6 H 4 < 2 ? } s prepared, practically, 
C(J 2 H 2 

by the oxidation of naphthalene. In the laboratory this is 

most easily effected by means of potassium permanganate, 

which yields, in an alkaline solution, phthalonic acid, 



262 ORGANIC CHEMISTRY. 

COCCLH 



C 6 H 4 < 



C0 9 H 



This may be considered as a derivative of oxalic acid, and 
is readily oxidized to phthalic acid by means of manganese 
dioxide in an acid solution. Commercially, phthalic acid is 
now prepared on a large scale by the oxidation of naph- 
thalene with fuming sulphuric acid.* Phthalic acid can also 
be prepared by the oxidation of orthoxylene, but not easily 

(P- 243)- 

When heated, phthalic acid is converted into an anhydride, 

CO 
C 6 H 4 < >0, which melts at 12 8°, and boils without de- 
composition at 2 8 4 . 

When phthalic anhydride is warmed with phosphorus 
pentachloride it is converted into phthalyl chloride, which 
appears, for the following reasons, to have, not the ordinary 

COC1 
structure of an acid chloride, C 6 H 4 < , but the unsym- 

metrical structure, 

CC1 2 

/ \ 

C 6 H 4 O. 

\ / 

CO 

When the chloride is reduced by means of zinc and hydro- 

PTT 

chloric acid it gives phthalid, C 6 H 4 < rn 2 > O, a lactone (p. 

318). Again, when the chloride is treated with benzene and 
aluminium chloride two phenyl groups are introduced in place 
of the chlorine. By reducing the resulting compound with 

* 100 parts naphthalene, 1500 parts sulphuric acid monohydrate, and fifty parts of 
mercuric sulphate are heated gradually from 200 to 250 and 300 till the phthalic 
anhydride has distilled. D. R. P. No. 91,202. 



PHENOL PHTHALEIN. 263 

zinc dust in an alkaline solution, a triphenylmethane car- 
boxylic acid is obtained, and distillation of this with barium 
hydroxide gives triphenylmethane itself. These facts can 
be satisfactorily explained only by the following formulae : 

C 6 H 4 < >0 -> C 6 H 4 N O^ C 6 H, X 

CO \CO/ C0 2 H 

Phthalyl chloride. Diphenyl phthalid. Triphenylmethane car- 

(Anhydride of triphenyl- boxylic acid, 

carbinol carboxylic acid*). 

m ~ > (QH 5 ) 3 CH. 

Triphenylmethane . 

Phenol Phthalein. — When a mixture of phenol and phthalic 
anhydride are warmed with concentrated sulphuric acid, 
phenol phthalein is formed, 

CO 

2 C 6 H 5 OH + C 6 H 4<co >0 = C 20 H 14 O 4 + H 2 0. 

Phenol. Phthalic anhydride. Phenol phthalein. 

C(C 6 H 5 ) 2 
When diphenyl phthalid, C 6 H 4 < > O , is treated with 

CO 
nitric acid a dinitro compound is produced. This, by reduc- 
tion, gives a diamino compound, and that, with nitrous acid, 
yields phenol phthalein. This demonstrates the structure 
of the phenol phthalein, as will be apparent from the fol- 
lowing : 



C(C 6 H 5 ) 2 




C(C 6 H 4 N0 2 ) 2 


C 6 H 4 < >0 


HNO3 


C 6 H 4 < >0 


CO 


-> 


CO 

Dinitro-diphenyl phthalid. 


C(C 6 H 4 NH 2 ) 2 




C(C 6 H 4 OH) 2 


C 6 H 4 < >0 


-> 


C 6 H 4 < >0 


CO 




CO 


Diamino-diphenyl phthalid. 




Phenol phthalein. 



^(C 6 H 5 ) 2 
* This name represents the acid, C — C fi H 4 C0 2 H, as a derivative of triphenyl car- 
\OH 
binol, (C 6 H 5 ) 3 COH. Carbiuolis a name synonymous with methyl alcohol, CH 3 OH. 



264 ORGANIC CHEMISTRY. 

Phenol phthalein is colorless, and undergoes practically no 
ionization in pure water. With alkalies it forms salts which 
ionize in water, and the ion, C 20 H 13 O 4 or C 20 H 12 O 4 , is, appar- 
ently, deep red in color.* As an unusually small number 
of hydrogen ions will prevent this ionization, phenol phthal- 
ein is especially suited for use as an indicator in titrating 
organic acids which undergo but little ionization. The same 
fact, however, makes it sensitive to the presence of carbonic 
acid, and it is necessary to use a standard alkali which is 
free from carbonates. 

When phenol phthalein is heated to 200 with sulphuric 
acid it is converted into hydroxyanthraquinone, 

CO. 
CO 



C 6 H 4 < nA >C 6 H 3 OH. 



ATT 

'Fluorescein. — By condensing resorcinol, C 6 H 4 < , 

with phthalic anhydride, fluorescein, 

C 6 H 3 -OH 

C < >0 

z v QH 3 — OH, 
QH 4 ( )0 
X CO X 

*This difference in color between solutions of the salt and of the acid has led some 
authors to consider that the salt is derived from an acid having a quinoid structure. 
O 



a jo ( 



c 

I 

COoH 



o 



A number of other facts pointing to this conclusion are known, but a discussion of them 
would lead too far. See Orndorff, A m. CJiem.J. 26, no. Also, Stieglitz, ./. Am. 
Chem. Soc. 24, 590. It seems altogether probable that in many cases the peculiar con- 
duct of indicators is due to a change in the ionization, which is associated with a differ^ 
ence in structure between a salt and the corresponding " pseudo acid " (p. 288). 



TEREPHTHAUC ACID 265 

is formed. This gives, with bromine, tetra-bromfluorescein 
(eosin). Compounds of the type of fluorescein are only 
formed when the two hydroxyl groups of the phenol are in 
the meta position and the third meta hydrogen of the 
phenol has not been replaced. 

Eosin and similar compounds, and also derivatives of 
anthraquinone prepared from phthaleins, are used as dyes. 

CO TT 
Isophthalic Acid, C 6 H 4 < 2 ? j s formed by the oxida- 
l^U 2 rl 3 

tion of metaxylene, or of any hydrocarbon having two side 

chains in the meta position. It may also be prepared from 

CO TT 
meta-aminobenzoic acid, C 6 H 4 <^t| > through the diazo 

compound and the cyanide (see p. 461). Isophthalic acid 
melts above 3cf6 , and yields no anhydride. The "cis " form 
of hexahydro-isophthalic acid, however, gives an anhydride. 

Terephthalic Acid, C 6 H 4 < _ r> 2 TJ , is formed by the oxida- 
CQ 2 Jbi 4 

CTT 
tion of paraxylene, C 6 H 4 < 3 , or cymene, 

CH 3 

C6H4< CH<^ 
CH 3 

It is most easily prepared from paratoluidine, 



QH 4 < 



CH 3 

nh; 



This, through the diazo compound and cyanide (p. 461), 
gives paratoluic acid, 

Wtt 4 < COH . 

The latter, by oxidation with potassium permanganate, gives 
terephthalic acid. Terephthalic acid is almost insoluble in 
water. When heated, it sublimes without melting. 



266 ORGANIC CHEMISTRY. 

Reduction Products of Terephthalic Acid. — Terephthalic 
acid can be readily reduced by means of sodium amalgam, 
and the reduction products have an especial interest, partly 
because they illustrate so clearly the possibilities of isomerism 
in compounds of this class, and partly because of the bearing 
which they have on the structure of benzene. 

The first reduction product is the A 2,5 dihy droterephthalic 
acid of the structure, 



H 


C0 2 H 

/ 2 


/ 

CH 


\ 
CH 


II 
CH 


II • 
CH 


\ 
C 


/ 


/ 
H 


\ 
C0 2 H 



This acid occurs in both the " cis " and " trans " form, and 
has all of the characteristics of an unsaturated compound 
with two double unions. 

By boiling with caustic soda it is converted successively 
into the A 1,5 acid, 



C0 2 H 

i 






C0 2 H 

i 


1 

c 

CH CH 

II 1 • 
CH CH 2 
\ / 
C 


and the A 14 


acid, 


i 
C 

CH 9 CH 

1 1 
CH CH 2 

^ / 
C 


H CQ 2 H 






1 
CQ 2 H 



REDUCTION PRODUCTS OF TEREPHTHALIC ACID. 267 

The A 13 dihydro acid is formed by treating the dibromide 
of A 2 tetrahydroterephthalic acid with alcoholic potash : 



H C0 2 H 
\ / 
C 


C0 2 H 

1 
C 


/ \ 
CH 2 CHBr 


CH 2 CH 


1 1 
CH 2 CHBr 


-> 1 1 
CH 2 CH 


\ / 
C 


\ // 
C 


/ \ 
H C0 2 H 


C0 2 H 



The three dihydroterephthalic acids last mentioned can 
show no " cis " and " trans " isomerism. (Why ?) 
The A 2 tetrahydroterephthalic acid, 



H 


C0 2 H 


\ 
C 


/ 


/ 

CH 2 


\ 
CH 


i 

CH 2 


II , 
CH 


\ 

C 


/ 


/ 
H 


\ 
C0 2 H 



is obtained by reducing either the A 1 3 or the A 15 dihydro- 
terephthalic acid. It exists in both the " cis " and " trans " 
forms. 

By boiling with sodium hydroxide the last acid is con- 
verted into the A 1 tetrahydroterephthalic acid, 



268 ORGANIC CHEMISTRY. 





C0 2 H 

i 




1 
C 


CH 2 


CH 


CH 2 


1 , 
CH 2 




\ / 
C 


H 


/ \ 

C0 2 H 



which can have but one stereomeric form. 

Further reduction of the last acid gives the " cis " and 
" trans " hexa-hydroterephthalic acids, 

H C0 2 H 

\ / 

C 

/ \ 

CH 2 CH 2 

I I . 

CH 2 (^H 2 

\ / 

C 
/ \ 
H C0 2 H 

This gives the ten theoretically possible reduction prod- 
ucts of terephthalic acid, and all of them have been pre- 
pared. In addition to these forms, several of the acids 
contain one or two asymmetric carbon atoms, and could, 
undoubtedly, be separated into optically active forms. 

Use of the Phthalic Acids in Determining the Structure 
of Aromatic Compounds. — Phthalic acid, isophthalic acid, 
and terephthalic acid have been of great importance as com- 



USE OF PHTHALIC ACIDS. 269 

pounds to which other compounds can be referred for the 
determination of their structure. The method which has 
been given (p. 105) for determining whether a given com- 
pound contains groups in the ortho, meta, or para position, 
while it is fundamental, is very tedious in its practical appli- 
cation. Having once determined the structure of a few 
benzene derivatives by that means, the structure of other 
compounds can usually be determined by a much shorter 
process. 

To illustrate : One of the bibrombenzenes, C G H 4 Br 2 , gives, 
on treatment with sodium and methyl iodide, a xylene, 

C 6 H 4 < 3 , which, on oxidation, yields terephthalic acid. 
LH 3 

The bibrombenzene was, therefore, a para compound. 

CC) TT 

Again: One of the sulphobenzoic acids, C 6 H 4 < 2 , gives 

0O3M 

phthalic acid when its sodium salt is heated with sodium for- 
mate, 

c ^4oSl + H - co * Na = c « H *<co£ a + Na * so *- 

CO IT 

The same salt gives salicylic acid, C 6 H 4 < 2 , when 

OH 

fused with caustic potash. Salicylic acid is, therefore, an 
ortho compound. It is to be remembered, however, that 
fusion with caustic potash often causes molecular rearrange- 
ments. 

Many bibasic acids with relatively less hydrogen than 
those which have been considered are known. Many 
acids containing three, four, five, six and more carboxyl 
groups are also known. None of these would involve 
principles of sufficient novelty to justify their consideration 
here. 



270 ORGANIC CHEMISTRY. 

General Methods of Preparing Acids. 
i. Oxidation of primary alcohols and aldehydes. 

R-CH 2 OH ~»R-C^ -> R-C^ 

2 \H \OH 

Alcohol. Aldehyde. Acid. 

2. Oxidation of secondary alcohols and ketones with open 
chain, giving monobasic acids with a smaller number of 
carbon atoms ; or of cyclic secondary alcohols and ketones, 
giving open-chain bibasic acids with the same number of 
carbon atoms. 

3. Oxidation of hydrocarbons, either unsaturated hydro- 
carbons which break down at the point of double union, or 
aromatic hydrocarbons, whose side chains can be oxidized in 
such a manner that only the carbon atom attached to the 
benzene nucleus remains. 

4. By distilling mixtures of the salts of alkyl esters of 
sulphuric acid, R — O — S0 2 — OH, or of sulphonic acids, 
R— S0 2 OH, with potassium cyanide, or by boiling aqueous 
or alcoholic solutions of primary, R — CH 2 — Br, or secondary, 

,>CHBr, halogen compounds, * with potassium cyanide, 
R 

followed, in each case, by the saponification of the cyanide 

with an acid or alkali. 

5. By treatment of a diazo compound of the benzene 
series with cuprous cyanide : 

2 R - N - CI + Cu 2 C 2 N 2 = 2 RCN + Cu 2 Cl 2 + 2 N 2 . 

Ill 
N 

The cyanide must, of course, be subsequently saponified. 

* In a few instances tertiary halogen compounds have been used, but the yields are 
very poor. 



GENERAL METHODS OF PREPARING ACIDS. 2J\ 

6. By condensation of carbon dioxide, or carbonyl chlo- 
ride, with an aromatic hydrocarbon by means of aluminium 
chloride : 

C 6 H 6 + COCl 2 + AlClg = C 6 H 5 C0C1 + A1C1 3 + HC1 

Carbonyl Benzoyl chloride, 

chloride. 

QH 5 COCl + H 2 = C 6 H 5 -C0 2 H + HC1. 

7. By condensing an aldehyde with the sodium salt of an 
acid in presence of the anhydride .of the acid (Perkin's 
synthesis). 

8. By condensing the sodium salt of malonic ester with a 
halogen compound (p. 252). 

9. Unsaturated acids are prepared by method 7 above ; 
by heating hydroxy acids ; by treating monohalogen deriv- 
atives of the acids with caustic potash ; and by reducing 
dihalogen derivatives in which the two halogen atoms are 
combined with adjacent carbon atoms. 

10. Many organic acids occur free, or in the form of 
glycerides or other esters, in nature, and so may be ob- 
tained from various natural products. 



Laboratory Exercises. 

Preparation of the following compounds : 

1. Formic acid. 

2. Isobutyric acid. 

3. Stearic acid. 

4. Acrylic acid. 

5. Benzoic acid from benzyl chloride : also from aniline. 

6. Cinnamic acid. 

7. Hydrocinnamic acid by reduction of cinnamic acid. 

8. Oxalic acid. 

9. Ethyl ester of malonic acid. 

10. Hydrocinnamic acid from malonic ester and benzyl chlo- 
ride. 



272 ORGANIC CHEMISTRY. 

11. Succinic acid. 

12. Pimelic acid. 

13. Camphoric acid ; camphoric anhydride. 

14. Phthalic acid ; phthalic anhydride. 

15. Phenol phthalein. 

16. Terephthalic acid. 



DERIVATIVES OF ACIDS. 273 



CHAPTER XIV. 

DERIVATIVES OF ACIDS. 

Only those derivatives in which the carboxyl is affected 
are characteristic of acids specifically, as distinguished from 
other substances, and only such derivatives will be con- 
sidered in this chapter. Hydroxy and ketonic acids will be 
made the subject of the following chapter, while halogen 
derivatives, sulphonic acids and other substances which are 
to be considered as substitution products of the acids will 
be discussed along with other compounds containing the 
same substituting groups. 

Acid Chlorides. 

When acids are treated with phosphorus trichloride or phos- 
phorus pentachloride, or when the salt of an acid is treated 
with phosphorus pentachloride, or phosphorus oxychloride, 
the chloride of an acid is formed. This contains one chlorine 
atom in place of one oxygen and one hydrogen atom, 
evidently in place of the hydroxyl group of the acid. 

3 CH 3 -C-OH + 2 PC1 3 = 3 CH3-C-CI + 3 HC1 + P 2 3 . 

Acetic acid. Acetyl chloride. 

C 6 H 5 C-0H + PC1 5 = C 6 H 5 -C-C1 + P0C1 3 + HC1. 

Benzoic acid. Benzoyl Phosphorus 

chloride. oxychloride. 

C 6 H 5 C0 2 Na4-PCl 5 =C 6 H 5 COCl4-POCl 3 + NaCl. 
2 CH 3 C0 2 Na+POCL = 2 CH.COCl + NaPO.+NaCl. 



274 ORGANIC CHEMISTRY. 

The anhydrides of bibasic acids often give unsymmetri- 
cal chlorides when treated with phosphorus pentachloride 
(p. 262). 

Acid fluorides, bromides, and iodides are also known, 
but have, relatively, very little importance. 

The chlorides of the acids are mostly substances which 
can be distilled without decomposition, and have a penetrat- 
ing, disagreeable odor. The boiling point is considerably 
lower than that of the acid from which the chloride is 
derived. Thus, acetic acid boils at 120 , acetyl chloride 
at 50. 9 . Benzoic acid boils at 249 , benzoyl chloride 
at 1 95 . 

The acid chlorides are decomposed by water with regene- 
ration of the acid. 

CH 3 C0C1 + H 2 = CH 3 C0 2 H + HC1. 

This decomposition takes place very easily with acetyl 
chloride and other chlorides of acids with low molecular 
weights, but much less quickly with benzoyl chloride and 
chlorides of acids of high molecular weight. In some cases 
when it is desired to regenerate an acid from the chloride of 
an acid which is itself liable to be decomposed by water 
(e.g., some brom acids) the decomposition can be effected 
with advantage by means of glacial formic acid. 

R-C0C1 + H 2 C0 2 = R-C0 2 H + HC1+C0. 

The chlorides of the acids are extremely reactive bodies, 
and are used in the preparation of anhydrides of the acids, 
esters and amides. (See below.) 

The chlorides of the acids are much more easily attacked 
by chlorine or bromine than are the free acids, and so are 
very often used in the preparation of halogen substitution 
products of the acids (p. 385). 



ACID CHLORIDES. 275 

When an acid chloride is mixed with a zinc alkyl, an 
addition product is formed : — 

CH 3 -COCl4-Zn / ™ 3 = CH 3 -C-0- 3 ZnCH 3 . 

If this product is decomposed by water a ketone results 
(p. 217). If, on the other hand, it is allowed to stand for 
some weeks with the same or a different zinc alkyl and the 
product is then decomposed by water, a tertiary alcohol and 
a saturated hydrocarbon are formed. 

/CH 3 
CH 3 -C-0-ZnCH 3 +Zn(C 2 H 5 ) 2 

\C1 

/ CH 3 
= CH 3 -C-OZnCH 3 +Zn / ^2i 1 5- 

* XC 2 H 5 ^1 

/CH 3 
CH 3 -C-OZnCH 3 +2 H„0 
\C 2 H 5 

/CH 3 
= CH 3 -C-OH + Zn(OH) 2 -fCH 4 . 
\C 2 H 5 

2-Methylbutanol-2 . 

If chlorides of aliphatic acids are mixed with anhydrous 
ferric chloride, hydrochloric acid is evolved, and on decom- 
posing the product of the reaction with water a ketone is 
formed. The first part of the reaction is doubtless similar 
to the syntheses by means of aluminium chloride (pp. 112 
and 198). 

2 CH 3 CH 2 - C - CI + FeCl 3 CI 

Propionyl chloride. | /O — FeCl 2 

= CH 3 -CH 2 -C-CH-CH 3 +HC1. 

I 
COC1 



276 ORGANIC CHEMISTRY. 

The reaction product, on treatment with water, would give 
the acid, 

CH 3 -CH 2 — CO— CH— CH 3 . 

I 
C0 2 H 

This acid, as a /?-ketonic acid (p. 351), would decompose into 
carbon dioxide and diethyl ketone, 

CH 3 CH 2 - CO - CH 2 CH 3 . 

Chlorides of acids may be reduced to aldehydes and 
alcohols. 

R_ COCWR- COH-»R— CH 2 OH. 
^O 
Acetyl Chloride, CH 3 — C — CI (ethanoyl chloride), is pre- 
pared by treating glacial acetic acid with phosphorus tri- 
chloride (see above). It boils at 50.9 . It has a very 
disagreeable, penetrating odor and is a very important 
reagent in the organic laboratory. 

//O 
Benzoyl Chloride, C 6 H 5 C , is prepared by treating ben- 
zoic acid with phosphorus pentachloride. It is prepared 
technically, and was also first prepared (by Liebig and 

Wohler) by acting upon benzaldehyde, C 6 H 5 C — H, with 
chlorine. Few, if any, other chlorides of acids have been 
prepared in this way. Benzoyl chloride boils at 195 . It 
is less easily decomposed by water than acetyl chloride. 

Acid Anhydrides. 

When the chloride of an acid is warmed with the sodium 
salt of the acid, an anhydride is formed : 

rrr CO 

CH3-COCI + CH 3 C0 2 Na= cH-CO >0 + NaQ 

Acetic anhydride. 



ACETIC ANHYDRIDE. 2JJ 

When monobasic acids of higher molecular weight are 
heated with acetic anhydride they are usually converted 
into anhydrides. 

2 C 3 H 7 C0 2 H + (C 2 H 3 0) 2 = (C 3 H 7 CO) 2 + 2 C 2 H 4 2 

Butyric acid. Butyric an- 

hydride. 

Bibasic acids in which the two carboxyl groups are sepa- 
rated by two or three carbon atoms form inner anhydrides 
on heating, or when warmed with acetic anhydride, acetyl 
chloride, phosphorus pentachloride, or phosphorus oxy- 
chloride. 

CO TT CO 

C 6 H 4 <^ 2 ^ + C 2 H 3 0C1 = C 6 H,< C0 >0+C 2 H 4 2 +HC1. 

Phthalic acid. Acetyl chloride. Phthalic 

anhydride. 

- Succinic acid and its derivatives form anhydrides more 
easily on heating than do glutaric acid and its derivatives. 

The anhydrides of the acids decompose with water, and 
regenerate the acids from which they are derived, though 
less easily than the acid chlorides. The different anhydrides 
exhibit much the same differences as the chlorides in this 
respect. A few of the " inner " anhydrides are so stable 
that they may even be crystallized from water without de- 
composition. 

The anhydrides of the monobasic acids have a higher 
boiling point than the acids themselves. Acetic anhydride 
boils at 1 36. 4 , benzoic anhydride boils above 400. 

With alcohols, ammonia and amines, anhydrides form 
esters and amides very much as acid chlorides do ; but 
their action is much more mild. 

Acetic Anhydride is by far the most important of the an- 
hydrides of monobasic acids, and is extensively used as a 
reagent in organic laboratories for the preparation of esters 



2/8 ORGANIC CHEMISTRY. 

and amides of acetic acid (usually called acetyl derivatives 
of the respective alcohols and amines) and in preparing the 
anhydrides of other acids. 

Phthalic Anhydride and some of its more important deriv- 
atives have already been considered (p. 262). 

Esters. 

Esters are derivatives of acids in which the hydrogen of 
the carboxyl has been replaced by some hydrocarbon radi- 
cal (an alkyl, alphyl, or aryl, p. 1 1 1) as C 2 H 5 , C 6 H 5 , etc. It is 
also often convenient to look upon them as alcohols in which 
the hydrogen of the hydroxyl has been replaced by an acid 
radical (an " acyl "). Thus, acetic ester may be considered 

as either ethyl acetate, CH 3 — C — O — C 2 H 5 , or as the acetyl 
derivative of ethyl alcohol, C 2 H 5 — O — C 2 H 3 0. 

In the earlier development of organic chemistry the esters 
were called " compound ethers," and such names as " acetic 
ether " and " benzoic ether " are still occasionally employed. 

The esters are, in structure, salts of the acids, and it is 
often convenient to name them as such. There is this very 
important difference between salts and esters, however, that 
salts usually undergo a high degree of ionization in solution 
and so react almost instantaneously with other acids, bases 
or salts, while esters undergo only a very trifling ionization, 
and usually react slowly. 

Preparation of Esters. — The more important methods for 
the preparation of esters are the following : 
1. Action of an acid upon an alcohol. 

C 2 H 5 -OH + H 2 S0 4 = C 2 H 5 -HSQ 4 + H 2 

Ethyl sulphuric acid. 

C 2 H 5 -OH + CH 3 C0 2 H = CH 3 C0 2 C 2 H 5 + H 2 0. 

Ethyl ester of 
acetic acid. 



PREPARATION OF ESTERS. 279 

The reaction is a reversible one, and, if equimolecular 
proportions of an acid and alcohol are used, proceeds only 
till a state of equilibrium is reached, the amount of ester 
finally formed depending upon the nature of the alcohol and 
acid, and only to a limited degree upon the temperature. 
The speed of the reaction, on the contrary, is highly depen- 
dent on the temperature. The general rule which applies 
to all reactions where the rate is dependent on the tem- 
perature is that the rate doubles for each increase of ten 
degrees. In accordance with the law of mass action an in- 
crease in the amount of the acid will increase the amount 
of ester which can be obtained from a given amount of 
the alcohol, or an increase in the amount of the alcohol will 
increase the amount of the ester which can be obtained 
from a given weight of the acid. The most effective means 
-for increasing the amount of the ester is to remove the 
water formed, and, in some cases, this can be practically 
accomplished. 

As the progressive formation of the ester or its decom- 
position can be readily followed by the titration of the 
residual acid, the reaction has been extensively used in 
studying the laws of mass action. The laws governing the 
formation of esters with different classes of alcohols and acids 
have also been carefully studied, and many interesting facts 
discovered. The rate of esterification is much slower for 

secondary monobasic acids, ( ,>CH — C0 2 H), than for pri- 
mary, (R— CH 2 — C0 2 H), and the rate is still slower for 

tertiary acids,! R' — C — C0 2 H). Aromatic acids, in which 

Vr"/ ' / 

the carboxyl is combined with the benzene nucleus, resem- 
ble, in general, the tertiary acids. The limit of esterification 



28o ORGANIC CHEMISTRY. 

with equimolecular amounts of acid and alcohol varies be- 
tween relatively narrow limits (67-76 per cent), being slightly 
higher for tertiary than for primary acids, which means, 
apparently, that the tertiary structure interferes relatively 
more with the decomposition of the ester by water than with 
its formation. With a given acid the rate of esterification 

is slower for a saturated secondary alcohol, (> CHOHj, 

than for a primary alcohol, (RHC 2 OH). The limit of esteri- 
fication is also lower for the secondary than for the primary 
alcohol. For the tertiary alcohol the rate is still slower, and 
the limit is very low indeed (in general only about 5 per cent 
of the ester being formed). 

V. Meyer's Law of Esterification. — In the aromatic series 
a very interesting law of esterification was discovered by 
Victor Meyer. In most cases aromatic acids are quite com- 
pletely esterified on boiling for a few hours with methyl 
alcohol containing a little hydrochloric acid. If, however, 
the aromatic acid contains two groups in the ortho position 
with regard to the carboxyl of the acid, the esterification is 
almost entirely prevented. Thus, mesitykne carboxylic acid, 
/CH 3 1 

C 6 H 2 r J 2 , gives, under the conditions mentioned, 
\ Cti 3 3 

\CH 3 5 
scarcely a trace of the ester. (Ber. d. chem. Ges. 27, 510, 
1580, 3146; 29, 1397.) 

The saponification of cyanides is also rendered very diffi- 
cult by the presence of two groups ortho to the cyanogen 
group. Other effects of a similar nature have also been 
noticed. 

2. By heating a mixture of an acid and alcohol with 
hydrochloric or sulphuric acid. The mixture is usually 



MEYER'S LA W OF ESTERFICATION. 28 1 

boiled with an upright condenser for some time, and, in 
general, only a small amount of the mineral acid (one to 
five per cent of the weight of the alcohol) is required. The 
reactions are the same as for the first method, the mineral 
acid remaining in the end unchanged. Its function is simply 
to hasten the reaction, and the laws which have been given 
as governing the reaction remain, in general, unchanged. 
It is commonly supposed that hydrochloric acid acts by the 
intermediate formation of an acid chloride. 

CH,C0 2 H + HC1 = CH 3 C0C1 + H 2 

CH 3 COCl + C 2 H 5 OH = CH 3 C0 2 C 2 H 5 + HC1. 

The sulphuric acid is supposed to form an alkyl sulphuric 
acid which then reacts with the acid to form the ester. 

C 2 H 5 OH + H 2 S0 4 = C 2 H 5 HS0 4 + H 2 
C 2 H 5 HS0 4 + CH 3 C0 2 H = CH 3 C0 2 C 2 H 5 4- H 2 S0 4 . 

Another explanation is that the alcohol adds itself to the 
acid forming a compound of the formula, 

/ O - C 2 H 5 
CH3-C-OH 
\OH 



This compound then loses water, and gives the ester, 
CH„- C 



^ / O - C 2 H 5 



The acid, in some manner not clearly explained, but prob- 
ably by the addition of its hydrogen ions to the oxygen of 
the acid, aids in forming the addition compound. The con- 
duct of the aromatic acids coming under V. Meyer's law 
decidedly favors this view. These acids, which cannot be 
esterified by means of methyl alcohol and hydrochloric acid, 
can be readily converted into esters by first preparing from 



282 ORGANIC CHEMISTRY. 

them the acid chloride or the silver salt (see below). It is 
difficult to explain this, if we suppose the function of the 
hydrochloric acid is to form the chloride of the acid, but if 
we suppose, instead, that the presence of the two ortho 
groups does not leave room for the ready formation of the 
addition compound, a satisfactory explanation is given. 
(V. Meyer, Ber. d. chem. Ges., 27, 510 ; 28, 2773.) 

It need scarcely be said that absolute alcohol is more 
suitable than ordinary alcohol for the preparation of esters 
by either the first or second method. 

3. By treating an alcohol with an acid chloride or anhy- 
dride, or with an acid chloride or anhydride and sodium 
hydroxide. 

C 6 H 5 COCl + C 2 H 5 OH = C 6 H 5 C0 2 C 2 H 5 + HC1 

(C 2 H 3 CO) 2 + C 2 H 5 OH = CH 3 C0 2 C 2 H 5 + C 2 H 4 2 

C 6 H 5 C0C1 + C 6 H 5 OH -f NaOH 

= C 6 H 5 C0 2 C 6 H 5 4- NaCl + H 2 

Phenyl benzoate. 

(C 2 H 3 0) 2 + C 6 H 5 OH + NaOH 

= C 2 H 3 O.OC 6 H 5 + NaC 2 H 3 2 +H 2 0. 

Phenyl acetate. 

The last two reactions are carried out in the presence of 
water, and are known as the " Schotten-Baumann " reaction. 
The acetyl and benzoyl derivatives of many substances con- 
taining alcoholic hydroxyl groups are crystalline bodies which 
can be easily purified, and so are admirably adapted for pur- 
poses of identification. The preparation of an acetyl or 
benzoyl derivative also serves in many cases to determine 
whether the oxygen of a given compound is in the form of 
hydroxyl or not, and, in other cases, to determine the num- 
ber of hydroxyl groups present. 

4. By treating the salt of an acid with an alkyl halide. 



SAPONIFICA TION. 283 

™<coi^ + 2 c ^ = c * HA< co£S + 2 A ^ 

Silver tartrate. Diethyl tartrate. 

The silver salts 4 and the alkyl iodides react, in general, 
most easily, but other salts and other halides are sometimes 
used. 

Saponification. — When esters are heated with water, acids 
or alkalies they are saponified or decomposed with the forma- 
tion of the free acid, or a salt of the acid, and the alcohol. 
Reactions of this type have already been spoken of for the 
glycerides (p. 230), and the closely analogous reactions for 
cyanides have been repeatedly noticed. The ease of saponifi- 
cation varies very greatly. In general, it seems to corre- 
spond with the ease of formation of the ester, those esters 
which are easily formed being easily saponified. The 
strength of the acid, as measured by its dissociation con- 
stant, is also an important factor in determining the ease of 
saponification, esters of strong acids being more easily 
saponified than the esters of weak ones. Ethers and esters 
both have a structure in which two carbon atoms are united 
by means of oxygen, and, just as it is not easy to draw a 
satisfactory line of distinction between acids and alcohols, 
it is also difficult to define sharply the line between ethers 
and esters. If we should say that esters can be saponified 
by alkalies, while ethers cannot, the distinction would cor- 
respond nearly, though not exactly, with the distinction 
already drawn between acids and alcohols (p. 221. See also 

P- x 43)- 

When the esters of derivatives of malonic acid are saponi- 
fied by means of acids (hydrochloric or sulphuric acid) the 
acids formed are often decomposed at the same time with 
evolution of carbon dioxide. In a similar manner /3-ketonic 



284 ORGANIC CHEMISTRY. 

acids (R-CO-CH 2 C0 2 H) decompose when their esters are 
saponified with acids, and sometimes when saponified with 
alkalies, giving ketones (p. 351). In these, and other cases, 
it is evident that the esters are more stable than the acids 
from which they are derived, and esters can often be distilled 
with little or no decomposition when the corresponding acids 
decompose easily. 

Just as methyl and ethyl ether boil at a lower temperature 
than methyl and ethyl alcohol, so the methyl and ethyl esters 
of acids boil at a lower temperature than the acids them- 
selves. Ethyl acetate boils at 77 , ethyl benzoate at 211 . 

Many of the esters of the acids and alcohols of the marsh- 
gas series have pleasant odors, and are extensively manu- 
factured for use in the preparation of artificial fruit essences. 
Isoamyl acetate has the odor of pears, octyl acetate that of 
oranges, ethyl butyrate that of pineapples, and is amy l-isov ale- 
rate that of oranges. A considerable number of esters are 
found in nature. The fats, which are esters of glycerol, 
have already been considered. 

OC TT 
Diethyl Carbonate, CO < 2 * , is prepared by treat- 
<J — C 2 H 5 

ing silver carbonate with ethyl iodide. It boils at 127 , and 

has a specific gravity of 0.9762 at — 5- 

4 

ATT 

Monoethyl Carbonate, CO < , is not known in the 

OC 2 H 5 

free state. Its sodium salt is formed by passing carbon 

dioxide into a solution of sodium ethylate in absolute 

alcohol. _ TT ^ XT , ^^ ^^ ONa 

C 2 H 5 ONa + C0 2 = C0 < oc H 

The free ester is probably formed when alcohol is left for 
a long time in contact with carbon dioxide under high pres- 



ACETAL. 285 

sure. The long continued effervescence of champagne is 
probably due to the slow decomposition of the ester into 
alcohol and carbon dioxide after the pressure is removed. 

Orthocarbonic Ester,* C(OC 2 H 5 ) 4 , is prepared by treating 
chlorpicrin, C0 3 N0 2 , with sodium ethylate. 

CC1 3 N0 2 + 4C 2 H 5 ONa = G (OC 2 H 5 ) 4 + 3 NaCl + NaN0 2 . 

The ester boils at i58°-i59°. 

Orthoformic Ester, H— C(OC 2 H 5 ) 3 , is prepared by treating 
chloroform with dry sodium ethylate, or by adding sodium 
to a mixture of chloroform, ethyl alcohol, and ether. 

CHC1 3 + 3 C 2 H 5 ONa = CH (OC 2 H 5 ) 3 + 3 NaCl. 

Acetal, or Ethylidene Diethyl Ether, CH 3 — CH < **, is 

OC 9 H 5 

/H 

formed by heating a mixture of acetaldehyde, CH 3 -C = 0, 
alcohol and acetic acid. It boils at 104 , and has a 

20° 

specific gravity of 0.8314 at -^. It is soluble in 18 vol- 

4 
umes of water at 25 . Acetal and similar compounds re- 
semble the esters in their method of formation, but are 
more like the ethers in their properties. They are gen- 
erally stable toward alkalies, but are easily decomposed into 
aldehyde and alcohol by acids. They are used in some 
reactions to advantage, in place of the less stable aldehydes. 
The compounds which have been given illustrate the great 
stability of the esters in comparison with the free acids, and 
that, while two hydroxyl groups can seldom remain com- 
bined with the same carbon atom, derivatives of such 
compounds are known in large number. 

* The prefix " ortho " in this sense is applied in naming an acid derived from an- 
other by the addition of water, as orthophosphoric acid, H 3 P0 4 , from metaphosphoric 
acidj HPO3. One molecule of water causes the formation of two hydroxyl groups. 



286 ORGANIC CHEMISTRY. 

Chlorformic Ester, or Chlorcarbonic Ester, CO < , is 

OC 2 H 5 

prepared by passing phosgene or carbonyl chloride into 

absolute alcohol. 

COCl 2 + C 2 H 5 OH = CO < ^ „ _ + HC1. 

U — C 2 H 5 

Chlorcarbonic ester boils at 93 . It has been used in the 
preparation of acids in a number of important syntheses. 

These esters have been selected rather because of their 
somewhat unusual character than for other reasons. The 
number of esters known is, of course, very great, but a 
further account of individual esters seems to be unnecessary 
here. 

Amides. 
Amides are prepared : 

1. By heating ammonium salts. 

//O /y O 

CH 3 -C-ONH 4 = CH 3 - C- NH 2 + H 2 0. 

Ammonium acetate. Acetamide. 

The reaction is probably to be interpreted as consisting at 
first in the dissociation of the salt into the free acid and am- 
monia, followed by the formation of the addition compound, 

/OH 
CH 3 — C — NH 2 , and finally by the loss of water. 

\OH^ 

2. By treating the chloride of an acid with ammonia, 

^o 

C H 5 COC1 H- 2NH3 = C,H 5 C- NH 2 + NH 4 C1. 

Benzamide. 

This method is especially suitable when the amide formed 
is insoluble or difficultly soluble in water. 

3. By treating an ester with ammonia, 



STRUCTURE OF THE AMIDES. 2%J 

C 6 H 5 C0 2 C 2 H 5 + NH 3 = C 6 H 5 CONH 2 + C 2 H 5 OH. 

Benzamide. 

4. By the partial saponification of cyanides or nitriles. 

C 6 H 5 CN + H 2 + HC1 = C 6 H 5 CONH, + HC1 
° r C 6 H 5 CN + H 2 + KOH = C 6 H 5 CONH 2 + KOH. 

^o 

5. Alkyl amides, R-C-NHR, are prepared by treating 
an acid chloride or anhydride with an amine and sodium hy- 
droxide. (Schotten-Baumann's reaction, p. 282.) 

C 6 H 5 -C0C1 -f- C 6 H 5 NH 2 + NaOH = 

C 6 H 5 C - NHC 6 H 5 + NaCl + H 2 0. 

Benzoic anilide. 

(C 2 H 3 0) 2 + C 6 H 5 NH 2 + NaOH = 

C 6 H 5 NH(C 2 H 3 0) + NaC 2 H 3 2 + H 2 0. 

Acetanilide. 

6. Alkyl amides are also formed by molecular rearrange- 
ment from the oximes of ketones, by treating them with 
phosphorus pentachloride. (Beckmann's rearrangement, 
p. 200.) 

C 6 H 5 - C - C 6 H 5 = C 6 H 5 - C - NHQH, 

II II 

N - OH O 

Oxime of benzophenone. Benzoic anilide. 

Structure of the Amides. — The structure of the amides 
follows from their formation from acid chlorides, and from 
cyanides, and from their saponification to acids. From 
these reactions it is evident that the nitrogen is combined 
with the end carbon atom, and does not lie between that 
carbon atom and the nucleus. The two formulae which 

//° 

would agree with these facts are, R — C v ^ TTT and 
& \ NH, 



CH 3 — C C 2 H 5 



288 ORGANIC CHEMISTRY. 

/ OTT 

R — C . The second formula would represent a sub- 

stance with acid properties, and so does not agree well with 
the ordinary properties of the amides. Nor does it agree 
with the existence of such compounds as ethyl-acetanilide, 

\N<~ 2 " 5 , in which the ethyl group is known to 

be combined with the nitrogen by the fact that it yields ethyl 

C TT 

aniline, 6 5 > NH, on saponification. The amides of strong 

acids do, however, form salts in which one hydrogen atom 
is replaced by a metal, and it is probable that these 

salts have the structure R — C x ^ TTT • The bromamides, 

R — C . ^ TrTT ^ , combine with ammonia in an ethereal solution 
\ NHBr 

to form salts, while in a solution in benzene they do not 

do this. This is most readily explained by supposing 

that in the free state these amides have the structure, 

//° 
R — C ^ XTTT , , but that in an ethereal solution this readily 
\NHBr J 

passes over into the tautomeric (see p. 297) form, 

/ OTT 

R — C v „„ , which would form with ammonia the salt 
^NBr 

R — C v „ 4 . Compounds of this type are called 
^NBr r J 

"pseudo" acids, as in the free state they are not acids at 

all. (Auwers, Ber. d. chem. Ges. 35, 228.) 

^o 

Assuming the formula R — C — NH 2 as representing the 
ordinary structure of the amides, they may be considered 
either as acids, in which the hydroxyl of the carboxyl group 
has been replaced by the amido ( NH 2 ) group, or as ammonia 



STRUCTURE OF THE AMIDES. 289 

in which one hydrogen atom has been replaced by an acid 
radical ( an acyl group ). The amines, on the other hand, are 
to be defined as alcohols in which the hydroxyl group is re- 
placed by the amino group (NH 2 ), or as ammonia in which 
one or more hydrogen atoms have been replaced by hydro- 
carbon radicals (alkyl groups). Unfortunately, the distinction 
here made between the prefixes amido and amino is not al- 

NH 

ways followed in the literature. Thus glycocoll, CH 2 < 2 

CO s H 

should, in accordance with this distinction, be called amino- 
acetic acid, since the NH 2 group is to be considered as 
replacing alcoholic and not acid hydroxyl, or it is to be con- 
sidered as combined with the hydrocarbon radical. It is 
often called, however, amidoacetic acid. The more logical 
nomenclature is now used by many careful writers. 

In a few cases two hydrogen atoms in ammonia have been 
replaced by acid groups, giving compounds of the type repre- 
sented by diacetamide, NH(C 2 H 3 0) 2 . Such compounds 
are comparatively rare and unimportant. Triacetamide, 
N(C 2 H 3 0) 3 , has also been prepared. 

Those bibasic acids in which the carboxyl groups are 

so situated as to form inner anhydrides (p. 254), form 

imides in which the connecting oxygen of the anhydride is 

replaced by the imido (NH) group. Thus, succinic acid 

CH 2 -CO 

gives succinimide, | > NH, and phthalic acid gives 

CH 2 -CO 

CO 
phthalimide, C 6 H 4 < > NH. The hydrogen of the imide 

group is sufficiently acid to be replaced by metals with 
the formation of well-defined salts, as, for instance. 

CO 

potassium phthali?nide, C 6 H 4 < >NK (or, possibly, 



290 ORGANIC CHEMISTRY. 

/OR 

C 6 H, N) The imides are, in general, such weak 

x CO ' 
acids, however, that their salts are decomposed by carbonic 
acid. It is noticeable that the derivatives of ammonia ex- 
hibit all gradations from the aliphatic amines (as CH 3 NH 2 ), 
which are strong bases in aqueous solutions and combine 
with acids to form stable ammonium salts, to the imides, 
some of which are comparatively strong acids. As acids it 
is possible, or probable, however, that the imides react in 
the tautomeric form, 

CxOH 



R ^N. 

\<x>/ 

/NH 2 
Urea, or Carbamide, C = , is the amide of carbonic 

\NH 2 
acid. It is of especial interest because it is to be looked 
upon as the final oxidation product of the proteins, and is 
the form in which most of the nitrogen of the food eaten 
leaves the human body. It is, further, of great historical in- 
terest as being the first " organic " compound prepared syn- 
thetically. In 1828 Wohler discovered its formation when 
a solution of ammonium cyanate, NH 4 — N = C = O, is evap- 
orated. The synthesis was the first step toward the over- 
throw of the view that compounds are formed in living bodies 
under the influence of a peculiar "vital force." It was the 
beginning of a long series of syntheses which have led to the 
conviction that the chemical and physical laws all apply 
equally to living and to dead matter, and that, while many 
of the processes which go on in living bodies cannot be imi- 
tated in our laboratories, there is no essential difference in 
character between laboratory syntheses and syntheses ef- 



UREA, OR CARBAMIDE. 29 1 

fected in living bodies. No reference is made here, of course, 
to the formation of organized structure, which is, apparently, 
something quite distinct from the formation of chemical com- 
pounds. 

The transformation is a reversible one, and its study has 
furnished an interesting confirmation of the laws which gov- 
ern reversible " mass " reactions. Walker and Hambly, /. 
Chem. Soc. 67, 751 ; Walker and Kay, Ibid, 71, 489. 

In addition to its preparation from ammonium cyanate, 
urea can be prepared by treating carbonyl chloride, 
COCl 2 , with ammonia, by heating ammonium carbamate, 

CO < / ^. XT ! J ' and by treating diethyl carbonate, CO < r ^ 2 TT 5 ' 

with ammonia. It will be noticed that these are simply 
applications of the first three general methods of preparing 
amides. 

Urea crystallizes from water, or from ethyl or amyl 
alcohol, in long prisms. It melts at 132 , and is easily 
soluble in water and in alcohol. 

Urea acts as a weak, monacic base. Urea nitrate, 
CON 2 H 4 .HN0 3 , is difficultly soluble in water, and is used 
in the separation of urea from urine. 

Urea also forms double salts with many inorganic salts. 
NaCLC0N 2 H 4 and Hg(N0 3 ) 2 . 4 CON 2 H 4 may be taken as 
types of these. A compound of especial interest is the one 
with mercuric nitrate and mercuric oxide, 

Hg(N0 3 ) 2 (CON 2 H 4 ) 2 . 3 HgO. 

This is formed on adding a dilute solution of mercuric nitrate 
to a solution containing urea, and is made use of for pur- 
poses of quantitative determination (Liebig). 

Urea is decomposed with evolution of nitrogen by a solu- 
tion of sodium hypobromite. 



292 ORGANIC CHEMISTRY. 

CO(NH 2 ) 2 4-3NaBrO = C0 2 + N 2 + 2H 2 + 3 NaBr. 

This reaction is also used for the quantitative determina- 
tion of urea. 

OH 
Carbamic Acid, CO< ATTT , is not known in the free state. 



NH, 



ONH 



Its ammonium salt, ammonium carbamate, CO < , is 

NH 2 

formed when ammonia and carbon dioxide are brought 
together, and is a constituent of commercial ammonium car- 
bonate. A freshly prepared solution of the ammonium salt 
gives no precipitate with calcium chloride, but, in solution, 
the salt gradually takes up water and changes to ammo- 
nium carbonate. 

CI 
Carbamic Chloride (urea chloride), CO < , is formed by 

IN ri 2 

passing phosgene (carbonyl chloride), COCl 2 , over ammonium 
chloride at 400 . It is also formed by the action of hydro- 
chloric acid gas on potassium cyanate. 

COCl + NH 4 Cl = CO<!? TT +2HCI 

KCNO + 2HCl = CO<^ T 1 TT + KC1. 
JNH 2 

Carbamic chloride is sometimes used in the synthesis of 

aromatic amides by Friedel and Crafts reaction. It has the 

advantage over carbonyl chloride, for the synthesis of acids, 

in that the amide group prevents the formation of ketones 

(p. 199). Derivatives of carbamic chloride, as phenyl car- 

Cl 
bamic chloride, CO < , are sometimes used for a 

N rIC c ri 5 

similar purpose. 

Urethane, or the Ethyl Ester of Carbamic Acid, is prepared 
from chlorcarbonic ester and ammonia, or from cyanic acid 
and alcohol. 



ALLOXAN. 293 



CI . ..„ __ NH, 



co <oc,h+ 2NH ^ co <oc;h +nh « c1 



C %0 t C2H5 ° H = CO< OC 2 H 5 - 

Cyanic acid. Urethane. 

Urethane crystallizes in leaflets which melt at 50 . It 
boils at 180 . 

Phenyl Urethane is formed when cyanformic ester is heated 
with aniline. 



™ + C.H,N„,.CO<™£H. 



Cyanformic ester. Aniline. Phenyl urethane. 

Phenyl urethane melts at 52 and boils at 238 . It crys- 
tallizes in needles. 

Uric Acid, C 5 H 4 N 4 O g , is to be considered as a derivative 
of urea. It was discovered by Scheele in 1776. The 
foundation for a knowledge of the relations of the body to 
other substances was laid by the classical research of 
Wohler and Liebig {Ann. d. Chem. (Liebig), 26, 241 (1838)). 
The present view of the structure of the body is based on 
the work of many different chemists, among whom may be 
mentioned especially Wohler, Liebig, Baeyer, Emil Fischer, 
Strecker, Medicus, and Behrend and Roosen. No attempt 
at a historical discussion of the development of knowledge 
of the body will be made, though such a discussion is of 
great interest, and would carry with it an epitome of the 
changing theories with regard to organic compounds. The 
interest of Wohler and Liebig in the body was doubtless oc- 
casioned by its occurrence in animal substances, and the 
important relation which it evidently bears to physiological 
processes. 

Alloxan. — When uric acid is oxidized with nitric acid, it 
gives alloxan, C 4 H 2 N 2 4 . 



294 ORGANIC CHEMISTRY, 

QH 4 N 4 3 + 40 = C 4 H 2 N 2 4 + C0 2 + N 2 + H 2 0. 

Alloxan crystallizes from water in long rhombic prisms, of 

the triclinic system. These contain four molecules of water, 

of which three molecules escape in dry air, while the fourth 

molecule is expelled at 150 . By boiling with alkalies it is 

,. ., PA COOH 
decomposed into urea and mesoxalic acid, CO < . 

CO OH 

This, together with the fact that alloxan is not an acid, 

r*c\ MTT 

establishes for it the formula CO<^^ ^ TTT >CO. The 

CO — NH 

form with one molecule of water undoubtedly is 

c(oh) 2 <^ : nh >CO; 

the presence of the negative groups giving relative stability 
to a compound having two hydroxyl groups combined with a 
single carbon atom. 

Alloxantin, C 8 H 6 N 4 8 +2H 2 0, is formed by the reduction 
of alloxan, and is to be considered as the pinacone (p. 188) 
of alloxan, having the structure, 

co <nS:co> c ( oh ) c (° h )<co:nS> co - 

NH-CO 
Parabanic Acid, CO < | , is formed by the further 

NH-CO 
oxidation of alloxan and by the oxidation of uric acid. Its 
structure is established by its decomposition by alkalies, 
which gives urea and oxalic acid. 

Structure of Uric Acid. — The series of syntheses which 
most clearly establishes the formula for uric acid depends on 
the formation of substances derived from uracil. 



STRUCTURE OF URIC ACID. 295 

NH-CH 
/ ^ 

CO CH. 

\ / 

NH-CO 

The mother substance, uracil itself, has not been prepared. 

Acetacetic ester combines with urea to form uramido 
crotonic ester. 



NH 2 CO-CH 3 

/ 1 
CO + CH 2 

\ 1 
NH 2 C0 2 C 2 H 5 

Acetacetic 
ester. 


= CO 


NH-C(OH)-CH 3 

/ 1 

CH 2 
\NH 2 | 

• C0 2 C 2 H 5 

NH-C-CHg 




= CO 


/ II 

CH 

\ 1 
NH 2 C0 2 C 2 H 5 

Uramidocrotonic ester. 



When the last compound is saponified with an alkali, 

and the resulting salt is treated with an acid, methy '/-uracil, 

NH-C-CH3 

/ II 

CO CH , is formed. 

\ I 

NH-CO 

Methyl uracil, on treatment with concentrated nitric acid, 
gives nitrouracil-carboxylic acid, 

NH-C-C0 2 H 

/ II 

CO C-N0 2 , 

\ I 

NH-CO 

and this loses carbon dioxide, when its aqueous solution is 
boiled, and forms nitrouracil, 



296 ORGANIC CHEMISTRY. 

NH-CH 
/ II 

CO C-N0 2 . 

\ I 

NH-CO 
This, by reduction with tin and hydrochloric acid, yields 
partly aminouracil, 

NH-CH 

/ II 

CO C-NH 2 , 

\ I 

NH-CO 
and partly, with an .elimination of the nitro group, oxyuracil 
{jsobarbituric acid), 

NH-CH 

/ II . 

CO C(OH). 

\ I 

NH— CO 

Oxyuracil gives, by oxidation with bromine water, dioxy- 

uracil (isodialuric acid), 

NH— C-OH NH-CH(OH) 

/ II / I 

CO C-OH or CO CO 

\ I \ I 

NH— CO NH— CO 

NH 

Dioxyuracil when warmed with urea, CO < 2 , and con- 

NH 2 

centrated sulphuric acid, is converted into uric acid, 

NH— C— NH 

/ II CO 

CO C-NH ' 

\ I 

NH-CO 

The relation between uric acid and alloxan, and the impor- 
tance of alloxan in the work which has led to a knowledge of 



TAUTOMERIC COMPOUNDS. 297 

the structure of uric acid, is apparent from the formula last 
given. 

Uric acid is a bibasic acid, forming both acid and normal 
salts, of which the sodium salts, NaC 5 H 3 N 4 3 +^H 2 and 
Na 2 C 5 H 2 N 4 3 +H 2 0, may be taken as types. In these salts it 
is evidently the hydrogen of the imido (NH) groups which 
is replaced, unless, as is possible, the salts are derived from 

the tautomeric ioxm 

NH-C-N . 
/ || X C-OH 

CO C-NH 7 

\ I 

N =C-OH 

Tautomeric Compounds. — The word tautomer was origi- 
nally used by Laar (I>er. d. chem. Ges., 18, 648 (1885)) to 
designate a class of bodies which react sometimes as though 
of one structure, and at other times as though of another. 
Laar's thought seems to have been that such substances pos- 
sess, in some sense, both structures. Since, in a number of 
cases, both forms of bodies of this class have been prepared, 
Laar's original interpretation of the phenomenon is no 
longer tenable. At most we can only suppose that in some 
cases both forms are present, and that each form passes 
readily into the other. Since the words tautomer and tauto- 
merism are more often used, and are more familiar than 
any others for the designation of this class of bodies, it 
seems desirable to retain them. The term will always be 
employed in this book with the understanding that a tauto- 
meric body may exist in two forms which are structurally 
different. In some cases it is extremely difficult to de- 
cide whether the common form of the body has the one or 
the other structure, or whether, perhaps, it is a mixture of 
the two forms. In other cases, both forms have been iso- 



298 ORGANIC CHEMISTRY. 

lated and their structure clearly established. In most cases 
tautomeric bodies are capable of existing in a ketone form 
(R— CO— CH 2 — ) and an " enol " (unsaturated alcoholic) 
(R— C(OH) = CH— ) form. 

NH— C— N . 
/ II CH 

Xanthine, CO C-NH 7 , Dimethylxanthine, or 

\ I 

NH— CO 

N(CH 3 )-C-N^ CH 
/ II / 

Theobromine, CO C— N — CH 3 , and Trimethylxan- 

\ I 

NH CO 

N(CH 3 )-C-N 



/ XH 



/ 

thine, or Caffeine, or Theine, CO C— N — CH 3 , are 

\ I 

N(CH 3 )-CO 

closely related to uric acid in structure, but differ from it very 
decidedly in their properties. While xanthine retains enough 
of the acid properties of uric acid to dissolve readily in a so- 
lution of potassium hydroxide, it is precipitated from such a 
solution by carbon dioxide, and it combines with hydrochlo- 
ric acid and strong mineral acids to form salts, of which the 
chloride, C 5 H 4 N 4 2 HC1, may be taken as a type. It is 
evident that the hydrogen of the NH which is between the 
two carbonyl groups gives to xanthine its very slight acid 
properties, while the NH combined with the CH gives the 
weak basic properties. Theobromine and caffeine are some- 
what stronger bases. Caffeine combines with two molecules 
of hydrochloric acid, but only the salt with one molecule of 
the acid is fairly stable. 

Xanthine is found in minute amount in the urine. Theo- 



PHTHALAMIDIC ACID. 299 

bromine is found in cacao ; caffeine is found in cacao, cof- 
fee, and tea. In large doses caffeine is a poison, but its 
effects can be overcome by artificial respiration. Xanthine, 
theobromine, and caffeine are classed as alkaloids, that is, 
as organic bases .which are found in nature. Each has 
been prepared synthetically. 

NH-C- N ^ 
/ II CH, 

Guanine, NH = C C— NH / , is found in guano. 

\ I 

NH-CO 

It is converted, by nitrous acid, into xanthine, the NH 

group being replaced by oxygen. 

^o 

Acetamide, CH 3 — C— NH 2 , is prepared by heating am- 
monium acetate for several hours at 2 2o°-2 3o° in a sealed 
tube, and distilling the mixture of water, ammonium acetate, 
and acetamide which results. Acetamide crystallizes in col- 
orless, odorless, rhombohedral crystals which melt at 82 ° and 
boil at 222 . It can be crystallized from benzene, in which 
it is difficultly soluble. It is very easily soluble in water 
and in alcohol. 

Acetamide is easily saponified to acetic acid and ammonia 
by alkalies, or even by boiling with water. Warming with 
phosphorus pentoxide converts it into methyl cyanide or ace- 
tonitrile, CH 3 CN, 

Benzamide, C 6 H 5 CONH 2 , is easily prepared by treating 
benzoyl chloride with aqueous ammonia. Benzamide crys- 
tallizes in leaflets which melt at 12 8°. It is difficultly solu- 
ble in water, easily soluble in alcohol. 

Phthaiamidic Acid, QH^ < 2 , is formed when phthalic 

C0 2 H 

anhydride is dissolved in aqueous ammonia. 



300 ORGANIC CHEMISTRY. 

c ^<co>° + 2NH » = c ^<co 2 nhV 

Cyanides or Nitriles. 

The cyanides have been so often referred to that they will 
require only a short notice here. They are prepared : 

i. By distilling a mixture of a salt of an acid ester of 
sulphuric acid, a salt of a sulphonic acid, or a halogen com- 
pound, with potassium cyanide. 

C 2 H 5 KS0 4 + KCN = CH 3 CH 2 CN + K 2 S0 4 

Ethyl sulphuric acid. Ethyl cyanide (Propiontirile). 

C 6 H 5 S0 3 K + KCN = C 6 H 5 CN + K 2 S0 3 . 

This method can only be applied, of course, when the 
cyanide can be distilled without decomposition. 

2. By boiling a halogen compound with potassium cyanide 
in an aqueous or alcoholic solution. 

C 2 H 5 Br + KCN = C 2 H 5 CN + KBr 

Ethyl cyanide. 

CI CN 

CH * < C0 2 Na + KCN = CH * < C0 2 N a + Ka - 

Sodium salt of cyanacetic acid. 

The reaction takes place readily only with primary 
(R — CH 2 X) or secondary ( >CHX) halogen compounds. 

Aromatic compounds in which the halogen is combined with 

(CTT \ 
as in C 6 H 5 Br or C 6 H 4 < 3 J will not react in 

this manner, but if the halogen is in the side chain the 
cyanide can be readily obtained. Thus : 

C H 5 CH 2 C1 + KCN = C 6 H 5 CH 2 CN + KC1. 

Benzyl chloride. Benzyl cyanide. 



CYANIDES OR NIT RILES. 30 1 

3. By treatment of amides with phosphorus pentoxide, 
phosphorus pentachloride, or acetyl chloride. 

CH s C-NH 2 +P 2 5 =CH 3 CN + 2 HPO s . 

Acetamide. Methyl cyanide. 

4. From isocyanides by rearrangement. 

C C H 5 N = C -» C g H 5 -C=eN. 

Phenyl isocyanide. Phenyl cyanide. 

5. From aromatic amines through the diazo compound 
(p. 461) with the use of cuprous cyanide. (Sandmeyer's 
reaction.) 

C 6 H 5 NH Q HC1 + HNOo = C 6 H 5 N = N + 2 H,0 

I 
CI 

Aniline chloride. Benzene diazonium chloride. 

2 C 6 H 5 - N = N + CuC 2 N 2 = 2 C 6 H 5 CN + 2 N 2 + Cu 2 Cl 2 . 

Phenyl cyanide. 

CI 

The structure of the cyanides is usually written R — C = N. 
The practically important feature of this formula is that the 
carbon of the cyanogen group is represented as combined 
directly with the hydrocarbon radical. This is demonstrated 
by the formation of the cyanides from the amides, by the 
ready saponification of cyanides to amides and acids, and 
by their reduction to amines (p. 422). 

The cyanides furnish a ready means of passing from 
primary and secondary alcohols, and from aromatic amines, 
to acids containing one more carbon atom, and for this 
reason are of very great practical importance. Because of 
this double relationship to the alcohol radical on the one 
hand, and to the acid on the other, they are called either 
cya,7iides or nitriles. Thus, CH 3 CN is called either methyl 
cyanide or acetouiti'ile. 



302 ORGANIC CHEMISTRY. 

The simple cyanides of not too high molecular weight are 
volatile, comparatively stable liquids which distill without 
decomposition. The cyanogen group has the same effect on 
an adjacent methylene (CH 2 ) group as has the carboxethyl 
group, for synthetical purposes (pp. 252 and 350). 

Hydrocyanic Acid, HCN, may be considered in some sense 
as the nitrile of formic acid, H — C0 2 H, and as such may be 
converted into formic acid by acids or alkalies. It also 
reacts, however, as an isocyanide, H — N = C (see below), and 
it is uncertain whether free hydrocyanic has the one or the 
other structure, or whether, possibly, it may not be a mixture 
of the two tautomeric forms (p. 297). 

Hydrocyanic acid is found in nature, in combination with 
benzaldehyde and glucose, in amygdalitis a bitter principle 
found in bitter almonds, peach stones, the leaves of the 
cherry and laurel, and in a number of other plants. When 
amygdalin is acted upon by the soluble ferment or enzyme, 
emulsin, it is decomposed. 

CN 
C 6 H 5 - CH < Q _ ^^q^ + 2 H20 

Amygdalin. = C 6 H 5 CHO + 2 C 6 H 12 6 + HCN. 

Benzaldehyde. Glucose. 

Pure hydrocyanic acid (prussic acid) is a volatile liquid 
which boils at 26. i°. It is a very violent poison. If moist, 
or in solution, it decomposes rapidly with the formation of 
brown amorphous substances. A trace of a mineral acid 
makes the solution more stable. Hydrocyanic acid is a 
much weaker acid than carbonic acid, though a stronger 
acid than phenol (p. 144). 

Potassium cyanide, KCN, is formed when nitrogen is 
passed over a heated mixture of potassium carbonate and 
carbon, apparently by the direct union of the three elements 



CYANOGEN CHLORIDE. 303 

of which it is composed. Potassium ferrocyanide, K 4 FeC 6 N 6 
+ 3H 2 0, which is still the chief commercial source of 
potassium cyanide and related compounds, is prepared by 
heating refuse nitrogenous organic matter, as blood, bone, 
leather scraps, etc., with potassium carbonate and iron 
turnings. A certain amount of cyanogen compounds are 
also recovered as a by product in the manufacture of illumi- 
nating gas. Potassium cyanide, or rather a mixture of 
potassium and sodium cyanides, is now made by heating 
the ferrocyanide with metallic sodium. 

K 4 FeC 6 N 6 + 2 Na = 4 KCN + 2 NaCN + Fe. 

The ferrocyanide is extensively used in making Prussian 
blue, and potassium cyanide is employed on a large scale in 
extracting gold from its ores. 

In the complex cyanides, of which potassium ferrocyanide, 
potassium ferricyanide, K 3 FeC 6 N 6 , and potassium silver 
cyanide, KAgC 2 N 2 , may be taken as types, the heavy metal 
combines with the cyanogen to form very stable groups 
which become the negative ion in solution. This can be 
demonstrated, experimentally, by the fact that the iron or 
silver of such solutions wanders toward the positive pole 
during electrolysis, and also by the fact that in such solutions 
iron or silver ions cannot be detected by the usual reac- 
tions. The formation of these complex ions is generally 
supposed to be due to a polymerization of the cyanogen 
group, but there can scarcely be said to be much positive 
evidence to support that view. 

Cyanogen Chloride, CNC1, is formed by the action of 
chlorine on hydrocyanic acid. 

HCN + C1 2 =CNC1+HC1. 

It is a volatile liquid which boils at 15.5 °. It polymerizes 



304 ORGANIC CHEMISTRY. 

easily, giving cyanuric chloride, C 3 N 3 C1 3 , which melts at 145 
and boils at 190 . 

Cyanogen chloride gives, with ammonia, cyanamide, 
C = N-NH 2 , or, more probably, H-N = C = NH. 

ISOCYANIDES OR ISONITRILES. 

The isocyanides are prepared : — 

1. By heating alkyl iodides with silver cyanide. 

C 2 H 5 I + AgNC = C 2 H 5 NC + Agl. 

Ethyl isocyanide. 

2. By treating a primary amine with chloroform and caus- 
tic potash. 

C 6 H 5 NH 2 +CHCl 3 + 3 KOH = C fl H 5 NC + 3 KCl+3 H 2 0. 

Aniline. Phenyl isocyanide. 

Isocyanides are also formed in small amount in the various 
methods of preparing cyanides. 

The isocynanides are generally liquids which boil at a 
lower temperature than the cyanides. They are violent 
poisons, and have an exceedingly disagreeable odor. 

The isocyanides combine with two atoms of chlorine or 
bromine to form compounds of which phenylisocyanide chlo- 
ride, C 6 H 5 NCC1 2 , is a type. This, on treatment with silver 
oxide, is oxidized to phenyl carbonimide, or phenyl isocyanate, 
C 6 H 5 N = C = O. Phenyl carbonimide is decomposed by 
water into carbon dioxide and carbanilide or diphenyl urea : 

2C 6 H-N = C = + H 2 = C0 2 +C0(^CH 5 ' 

Phenyl isocyanate Diphenyl urea. 

or phenyl carbonimide. 

Phenyl isocyanide also combines with hydrochloric acid 
to form the compound, 2 C 6 H 5 NC . 3 HC1. On account of 
this property of combining directly with halogen acids, the 
isocyanides were formerly called " carbylamines" but the 



ISOCYANIDES OR ISONITRILES. 305 

resulting compounds are decomposed by water, and do not 
comport themselves at all as ordinary salts. 

Phenyl isocyanide combines directly with sulphur to form 
phenyl isothiocyanate (phenyl mustard oil), C 6 H 5 N = C = S, 
and with hydrogen sulphide to form phenylthioformamide, # 

or thioformanilide, C 6 H 5 — NH — C v jr. This thioformani- 

lide is decomposed by caustic potash, giving aniline, potas- 
sium sulphide, and potassium formate. 

C 6 H 5 NH-<^KOH 

= C 6 H 5 NH 2 + K 2 S + HC0 2 K + H 2 0. 

The reactions which have been given to illustrate the 
chemical conduct of the isocyanides can only be satisfac- 
torily explained by supposing that the nitrogen in them is 
combined with the hydrocarbon radical. The isomerism of 
the cyanides and isocyanides is evidently due to the combi- 
nation of the radical with the carbon of the cyanogen in the 
former, and with the nitrogen in the latter. 

Phenyl cyanide is C 6 H 5 CN. 
Phenyl isocyanide is C C H 5 NC. 

For practical purposes these formulae answer almost all 
requirements. In further detail the formula of the cyanide is 
usually written C 6 H 5 — C = N. The formula for the isocyanide 
has often been written C 6 H' 5 NeeC. The direct combination 
with chlorine, bromine, sulphur, and hydrogen sulphide, the 
decomposition products of the resulting compounds, and 
especially the formation of phenyl carbonimide, can be better 
explained by the formula, C C H 5 — N = C. This formula 
represents the carbon as bivalent in the isocyanides. 

The formation of isocyanides from silver cyanide seems to 

* The student should notice the composition of these names, and explain them. 



306 ORGANIC CHEMISTRY. 

indicate that this compound has the formula, Ag — N = C, 
but the difficulty of determining whether the reaction in such 
cases is originally an addition or a substitution leaves the 
structure in doubt. The two reactions, 

Ag-N = C-J-C 2 H 5 I = C 2 H 6 N = C + AgI, 
and 

Ag-CEEN + C 2 H 5 I= A ^)C = N-C 2 H 5 

= AgI + C = N-C 2 H 5 , 

give the same final result, while the structures assigned to 
the silver cyanide are different. The difficulty met with here 
is characteristic of tautomeric substances, and illustrates the 
chief reason why the study of such compounds has been a 
very fruitful source of controversy. Since potassium cyanide 
gives ethyl cyanide, and not the isocyanide, when treated 
with ethyl iodide, it follows that either the structures of 
silver cyanide and potassium cyanide are different (e.g., 
Ag— N = C and K — C = N), or that the reaction is in one 
case a substitution and in the other case an addition. 

Cyanates and Isocyanates. 

When potassium cyanide is heated with lead oxide, or 
when dry potassium ferrocyanide is heated with potassium 
pyrochromate, potassium cyanate, KCNO, is formed. If we 
assume the formula K — N = C for potassium cyanide, potas- 
sium cyanate is probably K — N = C = 0. This formula also 
agrees best with the transformation of ammonium cyanate to 
urea (p. 290), but the demonstration of the formula meets 
with the same difficulty which attends the study of the cya- 
nides (see above). 

Ethyl Cyanate, C 2 H 5 — O — C = N, is formed when cyanogen 
chloride is passed into a solution of sodium ethylate. 



PHENYL ISOCYANATE. 30/ 

C 2 H 5 ONa + CNCl = C 2 H 5 -0 -C = N + NaCl. 

Ethyl cyanate is decomposed by alkalies into ethyl alcohol 
and potassium cyanate. 

C 2 H 6 — C = N + KOH = C 2 H 5 OH + KCNO. 

Both the method of formation and of decomposition indi- 
cate that the hydrocarbon radical of the cyanates is combined 
with oxygen. 

Ethyl Isocyanate, or Ethyl Carbonimide, C 2 H 5 N = C = 0, is 
formed when a mixture of ethyl potassium sulphate and 
potassium cyanate is distilled. 

KC 2 H 5 S0 4 +KCNO = C 2 H 5 — N = C = O -f K 2 S0 4 . 

The isocyanates give amines and carbon dioxide when 
treated with alkalies. 

C 2 H 5 N = C = O + 2 KOH = C 2 H 5 NH 2 + K 2 C0 3 . 

Ethyl amine. 

With water they give carbon dioxide and alkyl ureas. 

y AJTTp TT 

2 c 2 h 5 n=c=o+h 2 o = co; NHC ^+co 2 . 

Diethyl carbamide 
or diethyl urea. 

These reactions demonstrate that the radical is united with 
the nitrogen atom in the isocyanates, or, as they are better 
called, the carbonimides. 

Phenyl Isocyanate, or Phenyl Carbonimide, C 6 H 5 N = C = 0, 

may be prepared by passing carbonyl chloride (phosgene) 
over aniline chloride under pressure. 

C 2 H 5 NH 2 HC1 + C0C1 2 = C 6 H 5 N = C = + 3 HC1. 

It is a liquid with a penetrating odor and having a specific 
gravity of 1.092 at 15 . It boils at 166 . 



308 ORGANIC CHEMISTRY. 

Falminic Acid, C = N — O — H (?) When ethyl alcohol is 
treated with nitric acid and mercuric nitrate, mercuric ful- 
minate, HgC 2 N 2 2 , is found. This is used in percussion 
caps for firearms, and in fulminating caps for firing dynamite 
and gun-cotton. When mercuric fulminate is decomposed 
by hydrochloric acid it gives formic acid and hydroxyl- 
amine chloride. This decomposition indicates that it has 
the structure given above. 

C = N - OH + HC1 + 2 H 2 = ^ > C =0 + H a NOH.HCl. 

Formic acid. Hydroxylamine chloride. 

In 1823 Liebig demonstrated that silver fulminate, 
AgCNO, has the same composition as silver cyanate. This 
was the first case of isomerism discovered, and may be con- 
sidered as the first step toward the study of structure in 
chemistry. 

Thiocyanates. 

Corresponding to the cyanates, isocyanates, and closely 
related alkyl ureas, is a whole series of compounds in which 
the oxygen is replaced by sulphur. 

Potassium Thiocyanate, or, as it is more often called, 
potassium sulphocyanide, KCNS, is formed by heating a 
mixture of potassium cyanide and sulphur, or even by boil- 
ing a solution of potassium cyanide with sulphur. 

Ammonium Thiocyanate is formed by agitating a mixture 
of strong ammonia and carbon bisulphide. 

CS 2 + 4NH3 = NH 4 -SNC + (NH 4 ) 2 S. 
The thiocyanates are used commercially in dyeing. 

Ethyl Thiocyanate, C 2 H 5 — S — C = N, is prepared by dis- 
tilling a mixture of potassium ethyl sulphate and potassium 



ISOTHIOCYANATES. 309 

thiocyanate. Its structure is established by the formation of 
ethyl mercaptan, or a sulphur alcohol, by its reduction, and 
of ethyl sulphonic acid by its oxidation. 

C 2 H 5 S — GN + 6 H = C 2 H 5 SH -f- CH 3 NH 2 

Ethyl mercaptan. Methyl amine. 

C 2 H 5 S — CN -> C 2 H 5 — SO3H. 

Ethyl sulphonic acid. 

Isothiocyanates or Mustard Oils. — Carbon bisulphide com- 
bines with primary amines to form ammonium salts of 

SH 



dithiocarbamic acid, CS< 



nh; 



L 2 

CS 2 4- 2C 2 H 5 NH 2 = CS< 



SH.C 2 H 5 NH 2 
NHC.H,. 



Ethylamine. Ethyl ammonium ethyl 

dithiocarbamate. 



This ammonium salt gives, with mercuric chloride, a 
mercuric salt of ethyl dithiocarbamic acid. 



__ SHC 2 H 6 NH a 
2CS< NHC 2 H 5 +H ^ C1 



= ( CS< NHC 2 H r ), Hg + 2C2H5NH2 - HC1 - 

Mercuric ethyl 
dithiocarbamate. 

When this mercuric salt is heated it decomposes with the 
formation of an isothiocyanate. 

( CS <NHC 2 H 5 ) 2 H S = 2 C 2 H 5 N = C = S + H g S + H 2 S. 

The structure of the isothiocyanates follows both from 
their formation as just given, and from their decomposition 
by acids, which gives an amine and carbonyl sulphide. 

2 C 2 H 5 N = C = S + H 2 S0 4 + 2 H 2 

= (C 2 H 5 NH 2 ) 2 H 2 S0 4 + 2 COS. 

Ethyl ammonium sulphate. 



3IO ORGANIC CHEMISTRY. 

The isothiocyanates are substances with an extremely 
penetrating, disagreeable odor. As they are produced only 
from primary amines by the above reactions, their formation 
is sometimes used to distinguish primary from secondary and 
tertiary amines. 

Allyl Thiocyanate, CH 2 = CH-CH 2 -N = C = S, is found 
in the form of a glucoside of its potassium salt in mus- 
tard, and can be obtained from that source by fermentation 
(see amygdalin, p. 182). This occurrence of allyl thiocyan- 
ate has led to the designation of all of the thiocyanates as 
"mustard oils." 

Amide Chlorides, Imide Chlorides, Imido Esters, 
Amidines. 

By the action of phosphorus pentachloride on amides we 
should expect the formation of an amide chloride : 

/y O /CI 

R -C mlt +PC1 5 = R-C-C1 +POCI3. 
nWH 2 xN H 2 

Compounds of this type can, apparently, exist only when 
the two hydrogen atoms of the amide group have been 
replaced by hydrocarbon radicals. Otherwise they pass at 

once into imide chlorides, R — C , which may be con- 

sidered as acid chlorides in which oxygen has been 
replaced by the imide (NH) group. The imide chlorides 
are also formed by the action of hydrochloric acid on 

nitriles. 

r_C == N + HC1= R-C^ H 

Imido esters are obtained in the form of their chlorides 
by the action of dry hydrochloric acid upon a mixture of 



LABORATORY EXERCISES. 3 1 1 

equimolecular proportions of a nitrile and an alcohol diluted 
with ether. 

CH 3 - C = N + C 2 H 5 OH + HC1 = CH 3 - cf " * 

Amidines are formed by heating an amide in a current of 
hydrochloric acid, or by treating a chloride of an imido ester 
with ammonia. 

2CH 3 -CONH 2 +HCl=CH 3 -C(^ HC1 +CH 3 C0 2 H 

Chloride of acetamidine. 

The amidines are strong monacid bases. 

Amidoximes of the aliphatic series are formed by the union 
of nitriles and hydroxylamine. 

CH 3 CN + NH 2 OH = CH 3 C f ^ H 

The amidoximes are both weak acids and weak bases, 
forming salts both with metals and with acids. 

Laboratory Exercises. 
Preparation of the following substances : 

1. Acetyl chloride. 

2. Acetic anhydride. " 

3. Succinic anhydride. 

4. Acetic ester. 

5. Phenyl benzoate. 

6. Diethyl ester of tartaric acid. 

7. Urea. 

8. Uric acid. 

9. Alloxan. 
10. Acetamide. 



312 ORGANIC CHEMISTRY. 

ii. Benzamide. 

12. Phthalamidic acid. 

13. Ethyl cyanide. 

14. Phenyl cyanide from benzamide. 

15. Phenyl cyanide from aniline. 

16. Phenyl isocyanide (as a test tube reaction), 

17. Ammonium thiocyanate. 



GLYCOLIC ACID. 313 



CHAPTER XV. 

HYDROXY ACIDS. 

Hydroxy acids are, at the same time, acids and alcohols. 
As very many of the hydroxy acids and their derivatives 
form important natural compounds, a considerable number 
of them were discovered and studied long before their struc- 
tural nature was understood. As they differ from the simple 
acids from which they are derived only in containing an 
additional oxygen atom, they were very early called " oxy " 
acids. This term still clings to them, and to similar com- 
pounds, and is very often used in place of the more accu- 
rate designation, " hydroxy," partly for the historical reason 
given, partly because the longer prefix often seems more 
cumbersome. The prefix " oxy," with very few exceptions, 
really means " hydroxy." 

ACIDS, C„H 2n 3 . 

ATT 

Carbonic Acid, CO < , may be considered as hydroxy- 
OH 

formic acid, and so, as the first hydroxy acid. But just as 

the presence of only a single carbon atom causes formic acid 

to conduct itself partly as an aldehyde (p. 225), so carbonic 

acid is rather a bibasic acid than an alcohol (or hydroxy) acid. 

The more important derivatives of carbonic acid have 

already been considered (pp. 284 and 290). 

CO TT 
Glycolic Acid (ethanolic acid), CH 2 < 2 , is prepared : 



314 ORGANIC CHEMISTRY. 

CH 2 OH 

i. By the oxidation of glycol, I , or glycol alde- 

CH 2 OH 
CH 2 OH 

I 
hyde (ethanolal), C = . 



X H 



C0 2 H 



2. By boiling monochloracetic acid, CH 2 < , with 

water, or with marble dust and water. 

3. By treating glycocoll with nitrous acid, 

CH 2 <^ H + HN0 2 = CH 2 <^ H + N 2 + H 2 0. 

Glycocoll or Aminoacetic acid. Glycolic acid. 

4. From formaldehyde through the cyanhydrin (p. 178). 

H-C(J+HCN = CH 2 <™ 

Cyanhydrin of 
formaldehyde. 

CH 2 <^ + HC1 + 2H 2 = CH 2 <^ H + NH 4 C1. 

It will be noticed that the first method is simply one of 
the most common methods of preparing acids, while the 
second and third methods are common methods of preparing 
alcohols. The fourth method is a general method of prepar- 
ing a-hydroxy acids from aldehydes or ketones. 

Glycolic acid has been found in nature in green grapes, in 
the leaves of the wild grape-vine, and in beets. It crystal- 
lizes in needles or leaflets which melt at 8o°. It cannot be 
distilled without decomposition, and is only slightly volatile 
with water vapor. 

Glycolic acid is a moderately strong acid. 

For acetic acid, CH 3 C0 2 H, K = 0.0018. 

For glycolic acid, CH(OH)C0 2 H, K=o.oi52. 



LACTIC ACIDS. 315 

Esters and Ethers of Glycolic Acid. — Glycolic acid forms 
esters and ethers of the five types which can be predicted 
from its double nature as alcohol and acid. The following 
compounds are illustrations : 

Boiling Point. 

1. Ethyl glycolate CH 2 <g02C 2 H 5 160 

2. Ethyl ether of glycolic acid rw / C0 2 H o 

(Ethoxy acetic acid) uri2 ^ OC 2 H 5 

3. Glycolic acetate CH *<OC 2 HO 

4. Ethyl ether of glycolic ester rH / CO.,C,H a 

(Ethoxy acetic ester) Ln 2 ^ OC 2 H 5 

5. Ethyl ester of glycolic acetate CH 2 < qq 2 ^ q s I79 ° 

The chemical conduct of these bodies can be predicted 
from their structure. Thus 1, 3, and 5 can be completely 
saponified by boiling with alkalies, 4 can be half saponified, 
while 2 remains unaffected.. The ether groups may, how- 
ever, be decomposed by hydriodic acid (p. 167), giving ethyl 
iodide and glycolic acid. 

CH *<ogS 5 + HI = CH =<OH 2H + W 

Glycolid. — When glycolic acid is heated in a current of 
carbon dioxide at 210 , and subsequently distilled in a 
vacuum, it loses water and forms an anhydride glycolid. 

rnj r CH.-CO-O 

OH o - CO - CH 2 

Glycolid. 

Glycolid melts at 86°-87°. It crystallizes from alcohol in 
shining leaflets. 

Lactic Acids (a -hydroxy propionic acids, 2-propanolic acids), 

CH 3 — CH< Since a-hydroxypropionic acid contains 

C0 2 H. 



316 ORGANIC CHEMISTRY. 

an asymmetric carbon atom, it may exist in the right and 
left active forms, and in the racemic or inactive mixture of 
the two forms. 

^/-Lactic Acid, or Dextrolactic Acid, is found in extract of beef, 
is formed by the fermentation of milk sugar, cane sugar, 
or glucose under special conditions, especially by the fer- 
mentation of glucose under the influence of micrococcus acidi 
paralactici ; by the action of penicillium glaucum (which de- 
stroys the left-handed form of the acid) upon /-ammonium 
lactate ; and by crystallization of the strychnine salt of /-lac- 
tic acid, the salt of the leavo-acid crystallizing first. These 
methods of preparation are not so much of interest in them- 
selves as in illustrating common methods of preparing active 
compounds. 

/-Lactic Acid, or Laevolactic Acid, is formed by the fermenta- 
tion of milk sugar, cane sugar, glucose, or glycerol under the 
influence of the bacillus acidi laevolactici at a temperature of 
3 6°. It has also been prepared from the inactive acid by 
means of the strychnine salt (see above). 

/-Lactic Acid, or Racemic Lactic Acid, has been prepared syn- 
thetically by processes similar to each of the four methods 
given for glycolic acid (p. 314). The details need not be 
repeated. As is always the case with a synthetic compound 
prepared from inactive materials, the synthetic acid is inac- 
tive. The acid has also been prepared by the reduction of 
pyroracemic acid, CH 3 COC0 2 H, and by a great variety of 
both fermentation and chemical methods from various 
sugars. It is present in sour milk, and is often found in 
liquids which have undergone alcoholic fermentation. 

Pure /-lactic acid is a syrup which has a specific gravity of 



p-HYDROXYPROPIONIC ACID. 317 

o 

1.2485 at -~. It cannot be distilled without decomposition. 
4 

It is a moderately strong acid, K = 0.0138. 

When heated to 15 o° in a current of dry air, lactic acid is 
converted into an anhydride called ladid. 
CH3-CH-CO 
I I 

O O 

I I 

CO-CH-CH3. 

Lactid is an indifferent body. In contact with water it is 
slowly converted back to lactic acid. 

It melts at 124°, and boils at 255 . 

When lactic acid is distilled it decomposes into water, 
lactid, aldehyde, carbon dioxide, and carbon monoxide. 
With lead peroxide and sulphuric acid it gives aldehyde and 
carbon dioxide. This is one of the general methods of pre- 
paring aldehydes and ketones (p. 218), and is the reverse of 
the preparation of a -hydroxy acids through the cyanhydrin 
from aldehydes. Both reactions establish the structure of 
lactic acid. 

By heating with hydriodic acid, lactic acid is reduced to 
propionic acid. 

CH 3 CH(OH)C0 2 H + HI = CH s CHICO ? H + H 2 

a-Iodopropionic acid. 

CH 3 CHIC0 2 H + HI = CH 3 CH 2 C0 2 H -f I 2 . 

/3-Hydroxypropionic Acid (ethylene lactic acid, 3-propanolic- 
acid), CH 2 (OH)CH 2 C0 2 H, may be prepared through the 
following series of compounds : 
CH 2 OH CH.C1 CH 2 CN CH 2 C0 2 H 

CH 2 OH CH 2 OH CH 2 OH CH 2 OH. 

Glycol. Ethylene Ethylene Ethylene 

chlorhydrin. cyanhydrin. lactic acid. 



3 l8 ORGANIC CHEMISTRY. 

j3- Hydroxy propionic acid is a much weaker acid than the 
a-hydroxy acid, K = 0.0031 1. When heated, the acid de- 
composes with the formation of acrylic acid : 

CH 2 (OH)CH 2 C0 2 H = CH 2 = CH-C0 2 H + H 2 0. 

Acrylic acid. 

This decomposition is characteristic of /^-hydroxy acids in 
general, and distinguishes them from the a- and y-hydroxy 
acids. Some of the /3-hydroxy acids lose water even on 
heating with a solution of sodium hydroxide. 

/?-Hydroxybutyric Acid (3-butanolic acid), 

CH 3 CHOHCH 2 C0 2 H, 

is formed by the reduction of a cold dilute solution of acet- 
acetic acid, CH 3 COCH 2 C0 2 H. It is a syrup which decom- 
poses, on heating, into water and crotonic acid, 

CH 3 CH=CH-C0 2 H (see above). 

y-Hydroxybutyric Acid (4-butanolic acid). — The anhydride 
of this acid is formed by reducing an ethereal solution of 
succinyl chloride with sodium amalgam : 



CH,- CClo 


CH-CH, 


, " 2 >0 + 4 H 


= 1 2 ->0 + 2HCl. 


CH 2 - CO 


CH 2 -CO 


Succinyl chloride. 


Butyrolactone. 



Salts of the acid may be obtained by warming the anhy- 
dride, butyrolactone, with alkalies : 

CH 2 -CH„ 

I > O + NaOH = CH o (0H)CHoCH 2 C0 9 Na. 

CH 2 -CO 

The free acid is a liquid. It loses water very easily when 
warmed, and passes back into the lactone. The lactone is to 
be considered as a sort of " inner " ester, somewhat analogous 



y-HYDROXYlSOCAPROIC ACID. 319 

to the " inner " anhydrides of bibasic acids. The formation 
of such anhydrides, called lactones, is especially characteristic 
of y-hydroxy acids. A few similar lactones are known for 
acids in which the hydroxyl occupies the 8- or e-position with 
regard to the carboxyl, but only the y-lactones are common 
and easily formed. 

Not only do the y-hydroxy acids readily yield lactones, but 
the /3-y-unsaturated acids, when warmed with dilute sulphuric 
acid (1 : 1), pass over into the isomeric lactones. 

ptt C'TT 

r *>C=CH-CH 2 C0 2 H -» »>CH-CH 2 CH 2 -CO. 

o I 



A 3 Methyl-4-pentenoic acid Methyl-4-pentanolid 1.4 

(Pyroterebic acid). (Isocaprolactone). 

C H 9 C H 2 C H 2 
Butyrolactone (butanolid 1.4), | | , is an oil which 

O CO 

o 

boils at 206 , and has a specific gravity of 1.1286 at — %-. 

o 

It mixes with water in all proportions, but separates, from 
not too dilute a solution, on the addition of potassium car- 
bonate. It is easily volatile with water vapor. When 
treated with alcohol and hydrochloric acid, it gives the ethyl 
ester of y-chlorbutyric acid. 

CH 2 -CH 2 -CH 2 +HCl + C 2 H 5 OH = CH 2 -CH 2 C0 2 C 2 H 5 

O CO . CH 2 -C1 +H 2 0, 

Butyrolactone. Ethyl 7-chlorbutyrate. 

y - Hydroxyisocaproic Acid (4 - methyl - 4 - hydroxy - pentanoic 

CTT 
acid), 3 > C (OH) CH 2 CH 2 C0 2 H, is prepared by oxidizing 

CTT 

isocaproic acid, „ 3 > CHCHCHCO H, with an alkaline 
CH 3 2 2 - 



320 ORGANIC CHEMISTRY. 

solution of potassium permanganate at a temperature of 50 - 
6o°. In this, and several other similar cases, it is possible 
to oxidize a tertiary hydrogen atom directly to a hydroxyl 
group. The free hydroxy acid is not known, but when liber- 
ated it passes easily into isocaprolacto7ie, {methyl- \-pentano- 
lid 1.4), an oil which solidifies at a low temperature, and 
melts at io°. It boils at 208.5 , and resembles butyrolactone 
in its general properties. 

Acids, C w H 2w _ 2 3 . 

Comparatively few unsaturated hydroxy acids are known. 
When the grouping — C = CH — (" enol" form) occurs, it 

\OH 
generally passes readily into the " tautomeric " (pp. 297, 
349) — CO — CH 2 — (ketone form), and some of the more 
important acids of this class will be considered under the 
aldehyde and ketonic acids. When the double union and hy- 
droxyl groups are separated, as in a-allylhydroxybutyric acid, 

prr CT-rYOl-n 

r-TT 3 /^tt m j>CH- C0 2 H, compounds which are true 
Cti 2 = Uxi — CM 

unsaturated hydroxy acids may exist, but such acids exhibit 

no peculiarities which demand special mention. 

Cyclic hydroxy acids of this general formula correspond, 

in general properties, to the saturated hydroxy acids. To 

CO TT 

this class belong hexahydrosalicylic acid, C 6 H 10 < 2 , 

(JH 



and half a dozen acids, C 8 H 14 <^ TT 2 , derived from cam- 



C0 2 H 
OH 

phor. y-Hydroxy acids derived from cyclopentane and cy- 
clohexane form very stable lactones, but there is some 
evidence which indicates that such lactones are formed only 
from the trans form. The question is one which requires 
further experimental evidence. 



SALICYLIC ACID. 32 1 

Acids, C„H 3n G 3 . 

Very many hydroxy acids of the aromatic series are known, 
and many of them are important either in themselves or in 
their derivatives. 

Salicylic Acid, C 6 H 4 < 2 . The Reimer-Tiemann syn- 

thesis of salicylic aldehyde from phenol and chloroform has 
been given (p. 185). From the aldehyde the acid can be ob- 
tained by oxidation. If carbon tetrachloride is used instead 
of chloroform, salicylic acid will be formed, in part, though 
the chief product is parahydroxybenzoic acid : 

OX 
C 6 H 5 OH + CC1 4 + 6 KOH = C G H 4 < CQ K + 4 KC1 -f 4 H 2 0. 

Salicylic acid is also prepared : 

2. By heating sodium phenolate with carbon dioxide. 
The carbon dioxide at first forms sodium phenyl carbonate, 

CiC IT 

CO< 6 5 , a reaction exactly analogous to the formation 

of sodium salts of half esters of bibasic acids by means of 
sodium ethylate, (p. 255). If the sodium phenyl carbonate 
is heated in an autoclave, so that the carbon dioxide cannot 
escape, at i2o°-i3o° it is transformed to sodium salicylate : 

OC 6 H C0 2 Na 

CO< ONa - CA< OH * 

This method, which is used commercially, is not con- 
venient for the ordinary laboratory ; but if the sodium phenol 
carbonate is heated to i8o°-2oo° in a current of carbon 
dioxide, one-half of it is converted into salicylic acid : 

2 CO<^f=C 6 H 4 <^f + C 8 H 5 OH + CO, 
This is known as Kolbe's synthesis, and is quite general 



322 ORGANIC CHEMISTRY. 

in its application, the carboxyl group entering in the ortho 
position to the hydroxyl. If potassium phenolate is used in 
place of the sodium salt, salicylic acid is formed at 150 , 
but, curiously enough, at 220 parahydroxybenzoic acid, 

C0 2 H 1 

^^OH 4' 

is almost exclusively formed. 

3. By treating a salt of anthranilic acid (o-amino benzoic 
acid) with nitrous acid, and boiling the aqueous solution of 
the diazo compound formed (p. 460) : 

C0 2 H 1 CO.H 1 

^'^NH, 2 ^<h,<; oh 2 . 

Anthranilic acid. 

4. By fusing with caustic potash ; ortho-cresol, 

CH 

PIT 

ortho toluene sulphonic acid, C 6 H 4 <^q |t ; indigo ; or ortho- 

CC) TT 

sulphobenzoic acid, C 6 H 4 <oqVt. It is formed in small 

CO H 

amount by fusing orthochlorbenzoic acid, C 6 H 4 </^i 2 , or 

CO IT 

metabrombenzoic acid, C g H 4 <-d 2 , with caustic potash, 

the reaction being accompanied by a rearrangement, and 
giving, chiefly, metahydroxybenzoic acid in each case. In 
the first two cases above, the fusion with caustic potash 
is accompanied by an oxidation. 

The necessity of fusing the halogen derivatives of benzoic 
acid with caustic potash in the preparation of salicylic or 
metahydroxybenzoic acid illustrates a characteristic differ- 
ence between aromatic and aliphatic compounds. While 
chloracetic acid and similar compounds may usually be 



METAHYDROXYBEhlZOIC ACID. 323 

converted into hydroxy acids by merely boiling with solu- 
tions of alkalies, or even with water, aromatic compounds, 
with very few exceptions (p. 392), are not affected by such 
treatment. 

5. By saponifying methyl salicylate, 

r t-t ^ c 2 CH 3 

with caustic potash. Methyl salicylate is the chief constitu- 
ent of the oil of wintergreen. 

Salicylic acid crystallizes in needles, which melt at 15 6°. It 
has powerful antiseptic properties, resembling phenol in that 
regard, but without the disagreeable odor and highly poi- 
sonous character of the latter. It is often used as an anti- 
septic in wine, cider, and foods. Its use is objectionable as, 
while it is not an active poison, it interferes with digestion. It 
can usually be detected by extracting the acid solution with 
a mixture of ether and ligroin, separating, evaporating, and 
testing the residue with a dilute solution of ferric chloride, 
which gives, with salicylic acid (and with all <?r///<?-hydroxy 
aromatic acids), an intense violet color. Sodium salicylate 
is used as a remedy for rheumatism. 

When reduced with amyl alcohol and sodium, salicylic 

acid gives pimelic acid, 

CH 2 -CH 2 -CH 2 — C0 2 H 

I (P- 257)- 

CH 2 -CH 2 — C0 2 H 

Metahydroxybenzoic Acid (m-oxybenzoic acid), 

C0 2 H 1 

l « H ^OH 3' 
is prepared by fusing m-sulphobenzoic acid, m-brombenzoic 
acid, or m-chlorbenzoic acid with caustic potash, or by treat- 
ing metaminobenzoic acid with nitrous acid. It crystallizes 
in needles, which melt at 200 . 



324 ORGANIC CHEMISTRY. 

Parahydroxy benzoic Acid (p-oxybenzoic acid), 
/ C0 2 H i 
Q H 4 x + H 2 0, 

x OH 4 

can be prepared by the same general methods as the meta 
acid. It can also be obtained by the Kolbe synthesis at 
2 2o°, if potassium phenolate is used (see salicylic acid). 
When anethol (^p-allylmethoxybenzene), 

CHgCH = CH — C 6 H 4 OCH 3 , 

the chief constituent of anise-oil, is oxidized with nitric 
acid or chromic acid, anisic acid (p-methoxybenzoic acid), 

CO TT 

C 6 H 4 <Qpj^,is formed. This gives, with hydriodic acid, 

parahydroxybenzoic acid and methyl iodide. 

The last method of preparation may be taken as an illus- 
tration of methods which can often be used for the prepara- 
tion of similar compounds. The phenols are so unstable 
toward oxidizing agents that side chains which they may 

(PTT\ 
as in cresols, C 6 H 4 <qj^ 3 ) cannot be oxidized to 

carboxyl directly, as is done with other derivatives of 
benzene. By converting the hydroxyl group into an ether 
or an ester group (phosphoric or sulphuric esters, as 

C 6 H 4 < q _ 3 gQ jj, may be used), a compound sufficiently 
stable for oxidation is, however, formed ; and, after oxida- 
tion, the ether or ester group may be decomposed, giving 
the hydroxy acid which is desired. 

Paraoxybenzoic acid crystallizes with one molecule of 
water which it loses at ioo°. The anhydrous acid melts 
at 2io°. 

Salicylic acid is volatile with steam ; m- and p-oxybenzoic 
acids are not. 



contain 



GLYOXYLIC ACID. 325 

1. 

PTT 

Phthalid, C 6 H 4 <^q 2 >0, is a y-lactone of the aromatic 

2. 
series. It bears tlie same relation to phthalic acid which 
butyrolactone does to succinic acid, and may be prepared in 
a similar manner. 

p-Hydroxyisopropyl Benzoic Acid (4-methoethylol phen- 
methylic acid), C 6 H 4 < n/Qu\ < CH 3 , is prepared by oxidiz- 
ing an alkaline solution of cuminic acid (p-isopropyl benzoic 

C0 2 H 
acid), C 6 H 4 r Tj/CH 3 1, with potassium permanganate. 

XCH< CH 3 4 
This is another illustration of the oxidation of a tertiary 
hydrogen atom. The acid crystallizes in long, thin, triclinic 
prisms. It melts at 15 6°. By boiling with dilute hydro- 
chloric acid, or by treatment with acetyl chloride, it loses 
water and gives propenyl be?izoic acid, 

; co 2 h 1 

N \ CH 3 4 

ACIDS, C n H 2w 4 . 

The dihydroxy acids of the above formula are prepared 
by treating dihalogen substitution products of the fatty 
acids with moist silver oxide, or by oxidizing acrylic acid, 
CH 2 = CH — C0 2 H, or its homologues, with a cold, one per 
cent solution of potassium permanganate. 

Glyoxylic Acid (ethanediolic acid), CH(OH) 2 C0 2 H, is pre- 
pared by heating dibromacetic acid, CHBr 2 C0 2 H, with water, 
or by the oxidation of alcohol, glycol, or glycerol, with nitric 
acid. Glyoxylic acid is to be considered rather as the 



326 ORGANIC CHEMISTRY. 

hydrate of an aldehyde acid than as an ordinary hydroxy 
acid. It conducts itself as an aldehyde acid, forming an 
oxime (p. 179) and combining directly with ammonia, hydro- 
gen sulphide, and acid sodium sulphite. 

Glyceric Acid (propanediols acid), CH 2 OHCH 2 OHC0 2 H, 

is prepared by the careful oxidation of glycerol with nitric 
acid, or by warming a-/5-dibrompropionic acid, CH 2 BrCHBr- 
C0 2 H, with silver oxide and water. By warming with hy- 
driodic acid, glyceric acid is reduced to fi-iodopropio?iic acid. 
(See p. 409.) 

Glycidic Acid (epihydrinic acid), 
CH 2 

I >o 

CH 

I 
C0 2 H 

is formed by treating fi-chlorlactic acid, 

CH 2 C1CH(0H)C0 2 H, 

with caustic potash. It is a sort of inner ether, similar to 
ethylene oxide, 

CH 2 

I >o, 

CH 2 

and epichlorhydrin, CH 2 

I >o 

CH 

I 
CH 2 C1 

A considerable number of other compounds of the same type 
are known. Glycidic acid is volatile, and has a piercing 
odor. On boiling with water it gives glyceric acid. With 
hydrochloric acid it gives /3-chlorlactic acid. It is evident, 



TARTRONIC ACID. 327 

therefore, that although an ether in structure it is much less 
stable than open-chain ethers. Since ethylene oxide ex- 
hibits like characteristics, and since similar ethereal rings 
containing three or four carbon atoms with the oxygen atom 
are much more stable, it seems probable that the instability 
is due to tension within the ring (p. 194). 

CH(OH)(CH,) 7 CH 3 
Dioxystearic Acid, | , is prepared by 

CH(OH)(CH 2 ) 7 C0 2 H 

oxidizing oleic acid with a cold dilute solution of potassium 
permanganate. It crystallizes in leaflets, which melt at 
136. 5 . Further oxidation gives caprylic acid, C 7 H 15 C0 2 H, 
suberic acid, (CH 2 ) 6 (C0 2 H) 2 , and azelaic acid,(CH 2 ) 7 (C0 2 H) 2 . 
To avoid separating too far substances which are closely 
related, a somewhat less logical order will be followed in 
discussing the remaining hydroxy acids, which are to be 
mentioned. 

Tartronic Acid (hydroxymalonic acid), 

CH(OH)<J;°g+iHA 

is prepared by decomposing tartaric acid nitrate (" nitro- 
tartaric acid "), 

COOH 

I 
CH-N0 3 

I 
CH-NO3 

I 
COOH 



with dilute alcohol ; by the saponification of chlormalonic ester, 
CHC1<' 



C0 2 C 2 H s 



C0 2 C 2 H 5 



328 ORGANIC CHEMISTRY. 

with caustic potash ; and by the reduction of mesoxalic acid, 

Tartronic acid sublimes at a low temperature, and melts at 

i85°-i87°, decomposing at the same time into water, carbon 

dioxide, and glycolid (p. 315). 

CO IT 
Mesoxalic Acid, C(OH) 2 < 2 , is formed by boiling 

CO IT 

dibrommalonic acid, CBr 2 < 2 , with barium hydroxide, 

or by boiling alloxan with barium hydroxide (p. 293). Mes- 
oxalic acid crystallizes in needles which melt, with decom- 
position, at 120 . It illustrates, again, the possibility of 
two hydroxyl groups being combined with a carbon atom 
which is, at the same time, combined with strongly neg- 
ative groups. The concentrated solution is decomposed, 
by long boiling, into carbon dioxide and glyoxylic acid, 
CH(OH) 2 C0 2 H. This decomposition is closely related to 
the decomposition of acetoacetic acid, CH 3 COCH 2 C0 2 H, 

(P- 35 0- 

The barium and calcium salts of mesoxalic acid are very 

difficultly soluble in water. 

Malic Acid (hydroxy succinic acid), 

CH(OH)-C0 2 H 

I 
CH 2 — C0 2 H 

is found in apples, cherries, unripe grapes, tobacco leaves, 
and in a great variety of fruits and plants. It is prepared 
by treating either a-asparagine, 

NH 2 — CH-CONH 2 

I 
CH 2 C0 2 H 



MALIC ACID. 329 



$-asparagi?ie, C H 2 — C O N H 2 

I 



NH 2 -CH-C0 2 H 



or aspartic aa'd, NH 2 — CH — C0 2 H 

CH 2 C0 2 H 

.with nitrous acid, or by the partial reduction of tartaric 
acid with hydriodic acid : 

CH(OH)C0 2 H CH 2 — C0 2 H 

I +2 HI = I + I 2 + H 2 0. 

CH(OH)C0 2 H CH(OH) - C0 2 H 

Malic acid exists in two optically active forms, and in an 
inactive form. Some confusion has arisen in the designation 
of the two active forms from the fact that the natural acid, 
obtained from the berries of the European mountain ash, is 
laevo-rotatory in moderately dilute solutions, but becomes 
dextro-rotatory in concentrated solutions or in the presence 
of a strong mineral acid. The malic acid obtained by the 
reduction of dextro-tartaric acid shows an exactly opposite 
conduct. It would seem from this that the ion of malic 
acid which results from its dissociation in aqueous solution 
gives a rotation which is opposite to that of the molecules 
which are not ionized. On the other hand, it has been 
found that the acid which is dextro-rotatory in concen- 
trated solutions is laevo-rotatory in acetone. Whether it is 
also ionized in acetone has not, apparently, been determined. 
A further study of the relations involved seems desirable. 

Malic acid is reduced to succinic acid, 

CH 2 -C0 2 H 



CH 2 -C0 2 H 



by hydriodic acid. 



330 ORGANIC CHEMISTRY. 

When malic acid is heated for some time to i2o°-i3o°, it 
loses water, and gives fumaric acid, 

C0 2 H - C - H 

II 
H — C-C0 2 H 

If heated rapidly to 200 , maleic anhydride, 

II— C — CO 



x o, 



H-C — CO 

distills over. If we consider the two possible configurations, 

H H 

I I 

HO — C — C0 2 H HO - C - C0 2 H 

I and I , 

H — C - C0 2 H H - C — H 

I I 

H C0 2 H 

for malic acid, it will be seen that the first, in which the 
carboxyl groups are on the same side, would give maleic 
acid by the loss of water, while the second would give 
fumaric acid. From this it would seem that malic acid 
naturally assumes a configuration in which the carboxyl 
groups are not on the same side of the molecules. In the 
discussion of this and similar stereochemical problems the 
first configuration is called " unfavorable," the second 
" favorable " or " preferred " (German begiinstigi). 

Condensations with Malic Acid. — When a mixture of malic 
acid and phenol is heated with concentrated sulphuric acid, 
coumarin is formed. The malic acid seems to decompose at 
first into water, carbon monoxide, and an aldehyde acid, 

CHO 
I 
CH, -COoH 



TARTARIC ACID. 33 I 

The last compound condenses with the phenol in the ortho- 
position, to form phenylol-fi-hydroxypropionic acid, 

CH ^° H 
64 ^ CH(OH)CH 2 C0 2 H' 

and this gives coumarin, 

O - CO 

C 6 H 4 ( | , 

X CH=CH 

by loss of two molecules of water. Coumarin is a S-lactone. 
The acetyl derivative of the corresponding coumaric acid, 

OC 2 H 3 
6 4 ^CH = CHC0 2 H' 

is formed by heating a mixture of salicylic aldehyde, sodium 
acetate, and acetic anhydride ; and this, on further heating, 
loses acetic acid and passes over into coumarin. This prepa- 
ration of coumarin is of especial interest because it was the 
first illustration discovered of Perkin's synthesis (p. 244). 

Tartaric Acid (dihydroxy succinic acid), C 4 H 6 6 , is found in 
grapes, and in many plants and fruits, partly free, partly in 
the form of its potassium or calcium salts. The acid potas- 
sium salt, KC 4 H 5 6 , is difficultly soluble in water, and is 
much less soluble in dilute alcohol. It is deposited in wine- 
casks, and is known as argol in its crude form, or as cream of 
tartar when purified. The pure salt is mixed with sodium 
bicarbonate in some kinds of baking powders. 

The structure of tartaric acid was established in the fol- 
lowing manner. When tartaric acid is treated with hydro- 
chloric acid and alcohol, it is converted into a diethyl ester, 
C 4 H 4 6 (C 2 H 5 ) 2 , which can be purified by distillation under 
diminished pressure. This establishes the presence of two 
carboxyl groups, and gives the formula C 2 H 4 2 (C0 2 H) 2 . If 



332 ORGANIC CHEMISTRY. 

the diethyl ester is treated with acetyl chloride, or with 
acetic anhydride and sodium hydroxide (p. 282) a diacetyl 
tartaric ester, C 2 H 2 (OC 2 H 3 0) 2 (C0 2 C 2 H 5 ) 2 , is formed. This 
establishes the presence of two alcoholic hydroxyl groups, 
and gives the formula, C 2 H 2 (OH) 2 (C0 2 H) 2 . Finally, by 
reduction with hydriodic acid, tartaric acid has been con- 
verted into succinic acid, 

CH 2 -C0 2 H 

I 
CH 2 -C0 2 H 

This leads to the formula, 

CH(OH)C0 2 H 

I 
CH(OH)C0 2 H 

for the tartaric acid. The alternative formula, 

CH 2 -C0 2 H 

I 
C(OH) 2 -C0 2 H 

is excluded by the facts of the comparative stability of tar- 
taric acid, and of its optical activity (?). 

Tartaric acid contains two asymmetric carbon atoms. As, 
further, the molecule may be thought of as consisting of two 
exactly equal parts, the acid furnishes a very interesting 
illustration of the possibilities of optical isomerism. The 
theory indicates the following possibilities, which have been 
fully verified by the facts : 

I. The two halves may each turn the ray of polarized 
light to the right. This gives the ordinary or dext?-otartaric 
acid, which melts at i68°-i7o°. 

II. The two halves may each turn the ray to the left. 
This gives laevotartaric acid, melting at i68°-i7o°. 

III. A mixture of the first two acids in equal proportions 



TARTARIC ACID. 333 

is inactive, and is called racemic acid. Racemic acid was 
the first inactive compound to be resolved into its component 
active parts. In making a careful study of the acid, which 
is found as a by product in the preparation of tartaric acid, 
Pasteur noticed that the sodium ammonium salt deposited 
two kinds of crystals. These crystals exhibited hemihedral 
faces, which were so related that one crystal corresponded to 
the image in the mirror of the other. On examining the 
acid from these salts he found, to his surprise, that the acid 
from one set of crystals was dextrorotatory, while that from 
the other crystals was laevorotatory, (Ann. Chem. [3] 28, 56 
(1848)). This remarkable discovery must be considered as 
the first beginning from which the theories of stereochemistry 
were finally developed. The crystallization, to be success- 
ful, must take place at temperatures below 2 8°. Racemic 
acid melts at 2o5°-2o6°. It crystallizes with one molecule 
of water, while ordinaiy tartaric acid crystallizes free of 
water. Calcium racemate, Ca(C 4 H 4 O e ) 2 , is less soluble than 
calcium tartrate. The acid potassium salt of racemic acid 
is, however, more soluble than cream of tartar. 

Racemic acid can be prepared by mixing equal parts of 
dextro- and laevotartaric acid. It is also formed, together 
with mesotartaric acid (see below), when either of the tartaric 
acids is heated for some time with water at 175 , in a sealed 
tube. 

IV. If one-half of the molecule of tartaric acid turns the 
plane of polarized light to the right, and the other half turns 
it to the left, each will counterbalance the effect of the other, 
and an acid will be produced which will be inactive, and 
which cannot be separated into active forms. This is be- 
lieved to be the character of mesotartaric acid. Mesotartaric 
acid is formed, in part, when either of the tartaric acids is 



334 ORGANIC CHEMISTRY. 

heated with water to 165 for two days. If mesotartaric acid 
is itself heated to 200 till one-third of it is decomposed, a 
portion of it is converted into racemic acid. Mesotartaric 
acid melts at 139 — 143 . Its salts, also, differ from those of 
either of the other tartaric acids. 

The theory which has been given of the relation between 
the four tartaric acids finds a very interesting confirmation 
in their formation from fumaric and maleic acids. When 
fumaric acid is oxidized with a dilute solution of potassium 
permanganate, racemic acid is formed, while maleic acid 
gives, in the same manner, mesotartaric acid. (Kekule and 
Anschiitz, Ber. d. chem. Ges. 13, 2150; 14, 713.) 

OH H 

I I 

C0 2 H-C-H C0 2 H-C-H C0 2 H-C-OH 

II ->- ■ I and I 

H-C-C0 2 H H-C-C0 2 H HO-C-C0 2 H 

I I 

OH H 

Fumaric acid. Racemic acid. 

OH H 

I I 

H-C-C0 2 H H-C-C0 2 H HO-C-C0 2 H 

II ^ I and I 

H-C-C0 2 H H-C-C0 2 H HO-C-C0 2 H 

I I 

OH H 

Maleic acid. Mesotartaric acid. 

It can be seen from the formulae, and more clearly from 
models, that the forms produced from fumaric acid are 
optical isomers, while the forms from maleic acid are in- 
active by internal compensation and are identical. 

Both racemic and mesotartaric acid are formed when 
bibromsuccinic acid, 



CITRIC ACID. 335 

CHBrC0 2 H 

I 
CHBrC0 2 H. 

from fumaric acid,is treated with silver oxide and water. 
Isobibromsuccinic acid, from maleic acid, on the other hand, 
gives racemic acid only. These facts do not agree with the 
theory just given, and, together with a considerable num- 
ber of similar facts, are considered by some as evidence 
against the validity of the stereochemical theory which has 
been presented. While such a conclusion seems scarcely 
warranted in the face of the large mass of affirmative evi- 
dence which has been accumulated, such cases demonstrate 
the necessity of care in applying the theory, and show that 
molecular rearrangements which lead to conflicting results 
are especially liable to occur with this class of bodies. 

A large number of tartrates have been prepared. The 
most interesting are cream of tartar (see above), a similar 
acid ammonium salt, which is difficultly soluble, potassium 
antimonyl tartrate, or tartar emetic, 

KSbOC 4 H 4 6 + iH 2 0, 

the sodium ammonium salt, 

NaNH 4 C 4 H 4 6 + 4 H 2 0, 

and the sodium potassium salt, or Rochelle salt, 

KNaC 4 H 4 6 + 4H 2 0. 

Citric Acid (hydroxytricarballylic acid), 

CH 2 -C0 2 H 

c< 0H +H A 
I CO a H 



CH 2 -C0 2 H 



336 ORGANIC CHEMISTRY. 

is found in lemons, and in very many other natural products. 
It is obtained, commercially, from green lemons, the acid 
in the lemon juice being converted into the difficultly soluble 
calcium citrate, Ca 3 (C 6 H 5 7 ) 2 + 4 H 2 0, and the salt decom- 
posed with sulphuric acid. 

Citric acid has also been prepared synthetically in several 
different ways. When glycerol is treated with hydrochloric 
acid at i2o°-i3o°, symmetric dichlorhydrin, 

CH 2 C1CH(0H)CH 2 C1, 

is formed. This gives, by oxidation, a dichloracetone, 

CH 2 ClCOCH 2 Cl, 

and the latter, with hydrocyanic acid, the cyanhydrin, which 
can be saponified to dichloroxyisobutyric acid, 

c2;c!> c ( oh > co * h - 

This, with potassium cyanide, gives the dicyanide, from which 
citric acid is obtained by saponification. The transforma- 
tions will be clearer from the following diagram : 

CH 2 OH CH 2 C1 CH 2 C1 CH 2 C1 CH 2 C1 

' I ' I OH ' OH 

CHOH -> CHOH -> CO ~> C < „_ T -> (:<__.__ 

II C °2 H 

CH 2 OH CH 2 C1 CH 2 C1 CH 2 C1 CH 2 C1 

CH 2 CN CH 2 C0 2 H 

I OH 'OH 

~* | C0 2 H | C0 2 H* 

CH 2 CN CH 2 C0 2 H. 

Citric acid crystallizes from water in rhombic prisms which . 
contain one molecule of water of crystallization. It is solu- 



CITRIC ACID. 337 

ble in three-fourths of its weight of cold water. The anhy- 
drous acid melts at 153 . 

If citric acid is heated to 175 it loses water, and gives 
aconitic acid, 

CH 2 C0 2 H 
I 



CHC0 2 H 

At a higher temperature the aconitic acid decomposes, giv- 
ing itaconic acid, 

CH 2 -C0 2 H 
I 
CH 2 = C C0 2 H 

and also, by rearrangement, cifraconic acid, 

H -C-C0 2 H 

II 
CH 3 -C-C0 2 H 

or their anhydrides. Aconitic acid can be reduced to tri- 
carballylic acid, 

CH 2 C(XH 

I 
CH-C0 2 H, 

I 
CH 2 C0 2 H 

by sodium amalgam. 

When warmed on the water-bath with concentrated sul- 
phuric acid, citric acid is decomposed into formic acid and 
acetone dicarboxvlic acid, 

CH 2 C0 2 H 
I 

c=o 

I 

CH 2 C0 2 H 



338 ORGANIC CHEMISTRY. 

the formic acid decomposing, further, into carbon monoxide 
and water. 

With manganese dioxide and sulphuric acid it is oxidized 
to acetone and carbon dioxide. (Why? See pp. 217 and 

35 1 -) 

Both citric acid and its salts are extensively used. A 
concentrated solution of the neutral ammonium salt, (NH 4 ) 3 - 
C 6 H 5 7 , is used in the analysis of fertilizers to dissolve 
" citrate-soluble " (formerly called " reverted ") phosphates. 
A mixture of ferric ammonium citrate, 

(FeC 6 H 5 7 -h(NH 4 ) 2 C 6 H 6 7 or FeC 6 H 5 7 + NH 4 C 6 H 7 7 ), 

and potassium ferricyanide is used in the preparation of the 
ordinary " blue print " paper, the reducing action of the citric 
acid converting the iron to the ferrous state under the action 
of sunlight. 

At least eleven acids of the formula, 

CH(OH)-C0 2 H 

I 
CH(OH) 

CH(OH) 

I 
CH(OH)-C0 2 H 

are known. These differ, apparently, in the relation between 
the asymmetric carbon atoms which they contain. The gen- 
eral structure has been established by the reduction of most 
of them to adipic acid (CH 2 ) 4 (C0 2 H) 2 . 

The most important of these acids are saccharic and mucic 
acids. 

Saccharic Acid exists in the two optically active forms and 
in the racemic form. The dextrosaccharic acid is formed by 



PROTOCATECHUIC ACID. 339 

the oxidation of cane-sugar, milk-sugar, raffinose, starch, or 
glucose by means of nitric acid. As all of these substances 
yield ^/-glucose, CH 2 OH 

(CHOH)' ,H , 

' . >o 

as one product of their hydrolysis with acids, ^f-saccharic 
acid must be considered as the normal oxidation product 
of that body. 

Mucic Acid is formed by the oxidation of some gums, raffi- 
nose or melitose, milk-sugar, dulcite, quercite or galactose by 
nitric acid. As all of these substances except quercite give 
galactose by hydrolysis, or may be prepared from galactose,* 
mucic acid is to be considered as the normal oxidation prod- 
uct of that substance. Galactose differs from glucose only 
in configuration, the structural formulae being otherwise 
identical. 

Both saccharic and mucic acids and all isomeric acids, 
which differ from them only in configuration, give dehydro- 
mucic acid, CH = C — C0 2 H 

I >o 

CH = C-C0 2 H 

when heated to 150 with concentrated hydrochloric acid. 
When heated to a higher temperature, this decomposes into 
carbon dioxide and pyromucic acid, 

CH = CH 
I >0 

CH = C-C0 2 H 

Protocatechuic Acid (3.4 dihydroxybenzoic acid), 

^ C0 2 H 1 
C 6 H 3 -OH 3, 

^OH 4 

* Dulcite is formed by the reduction of galactose. 



340 ORGANIC CHEMISTRY. 

is prepared from vanillin by fusion with caustic potash 
(p. 1 86). It is also formed by fusing sulphanisic acid, 



/C0 2 H 


i 


C 6 H 3 — S0 3 H 


3> 


^OCH 3 


4 


or fi-cresol sulphonic acid, 




^C0 2 H 


i 


C 6 H 3 -S0 3 H 


3> 


^OH 


4 



with caustic potash. It crystallizes in monoclinic needles, 
which melt at 199°, with decomposition. The acid decom- 
poses, on distillation, into carbon dioxide and pyrocatechol, 

CsH4< OH 2 

Protocatechuic acid can be prepared from vanillin (p. 
186), asafoetida, myrrh, and a considerable number of other 
natural substances. Its methyl ether, 



^C0 2 H 
C 6 H 4 — O C H 3 
^OH 

is called vanillic acid. 


1 

3> 

4 


Gallic Acid, 


C0 2 H 1 

CH< OH 3 

OH c 


+ H 2 0, 



is prepared by boiling tannic acid with dilute acids. It is 
also formed by fusing dioxybrombenzoic acid, 



C 6 H 2 < 



C0 2 H 1 

OH 3 

Br 4' 

OH 5 



with caustic potash. Gallic acid melts with decomposition 



GENERAL PROPERTIES OF HYDROXY ACIDS. 34 1 

at 220 — 240 . It decomposes, on distillation, into carbon 
dioxide and pyrogallol (p. 160). 

Tannin, C M H 10 O 9 + 2 H 2 0, is found in oak bark, sumach, 
tea-leaves, canaigre root, and a great variety of other sub- 
stances. It has 'been prepared by heating gallic acid with 
phosphorus oxychloride : 

2 C 7 H 6 O 5 -H 2 O = C 14 H 10 O 9 

Gallic acid. Tannin, or 

Tannic acid. 

Tannin forms an insoluble compound with albumin ; also 
with the corium of animal skins, converting them into leather. 

General Methods of Preparing Hydroxy Acids. 

The general methods of preparing hydroxy acids are 
essentially the same as those for preparing alcohols (p. 161). 
The only methods of preparation peculiar to the acids are 
the Reimer-Tiemann reaction, using phenol and carbon 
tetrachloride ; Kolbe's reaction of a sodium or potassium 
phenolate and carbon dioxide ; the formation of a lactone 
from a /?-y-unsaturated acid by boiling with dilute sulphuric 
acid ; the oxidation of a tertiary hydrogen atom ; the reduc- 
tion of the unsymmetrical chloride of an " inner " anhydride ; 
and the preparation of a-hydroxy acids from aldehydes and 
ketones, through the cyanhydrins, 

R >c< 0H 

R >U< CN 

General Properties of Hydroxy Acids. 

The general properties of hydroxy acids are, in part, 
merely the same as those of alcohols. Thus primary 
hydroxyl groups may be oxidized to aldehyde and carboxyl 
groups. Secondary hydroxyl groups may be oxidized to 
ketone groups. If the resulting ketone group is in the 



342 ORGANIC CHEMISTRY. 

a-position, further .oxidation gives an acid with one less 
carbon atom ; if in the ^-position, the ketonic acid is 
unstable (p. 351), and loses carbon dioxide with formation 
of a ketone. As y-hydroxy acids readily form lactones, it 
is usually necessary to convert them into esters before 
oxidation. 

Besides the oxidation to ketonic acids, which can some- 
times be effected, a-hydroxy acids may be oxidized to alde- 
hydes or ketones and carbon dioxide by means of lead 
peroxide or manganese dioxide and sulphuric acid. 

a-Hydroxy acids do not form lactones or inner anhydrides, 
but do form anhydrides from two molecules of the acid, such 
anhydrides containing a ring of four carbon and two oxygen 
atoms. If, however, the a-carbon atom bears no hydrogen, 
such anhydrides are not formed, but the acid may distill with- 
out decomposition. 

/3-Hydroxy acids very rarely form lactones. They lose 
water easily, and give a-/3-unsaturated acids. 

y-Hydroxy acids readily form inner anhydrides, called 
lactones. S-Lactones are much less common, and very few 
e-lactones have been prepared. 

Phosphorus trichloride, phosphorus pentachloride, and the 
tribromide and pentabromide, when they act upon hydroxy 
acids, replace the alcoholic as well as the carboxyl hydroxyl 
with chlorine or bromine. 

CH 3 CH(OH)C0 2 H + 2 PC1 5 

Lactic acid. 

= CH3CHCICOCI+2 POCl 3 + 2 HC1. 

Chloride of a-chlor- 
propionic acid. 

In many cases the hydroxyl group in aliphatic or alicyclic * 

* Derivations of cyclopropane, cyclobutane, etc., are called " alicyclic" compounds, 
because their general chemical conduct resembles that of the aliphatic, and not that of 
the aromatic compounds. 



LABORATORY EXERCISES. 343 

compounds can be replaced by merely treating them with 
strong hydrochloric or hydrobromic acid. 

By heating with hydriodic acid, aliphatic or alicyclic 
hydroxy acids may be reduced, the hydroxyl being replaced 
by hydrogen : 

CH 3 CH(OH)C0 2 H + 2 HI = CH 3 CH 2 C0 2 H + I 2 + H 2 0. 

Ortho-hydroxy acids, in the aromatic series, give a violet 
color with ferric chloride, meta- and para-hydroxy acids do 
not. 

Unsaturated hydroxy acids of the general formula, 

R-C(OH) = CH-C0 2 H, 

also give a violet color with ferric chloride, while the tauto- 
meric form, R— CO — CH 2 C0 2 H, when sufficiently stable to 
have an independent existence, does not do this. The esters 
of these acids conduct themselves in a similar manner. 

Laboratory Exercises. 
Prepapation of the following : — 

1. Glycocoll. 

2. Glycolid. 

3. Isocaprolactone, starting with amyl alcohol. 

4. Salicylic acid, two ways. 

5. Parahydroxybenzoic acid. 

6. Phthalid. 

7. Diacetyl derivative of the diethyl ester of tartaric acid. 

8. Mandelic acid. 



344 ORGANIC CHEMISTRY. 



CHAPTER XVI. 

KETONIC AND ALDEHYDE ACIDS. 

As has already been pointed out, the ketonic and aldehyde 
acids are isomeric with the unsaturated hydroxy acids. So 
far as the two classes of compounds are " tautomeric," the 
unsaturated hydroxy acids will also be discussed in this 
chapter. 

Glyoxylic Acid, CH(OH) 2 C0 2 H, which is to be considered 
as the simplest aldehyde acid, has already been considered 

(P- 325> 

Pyroracemic Acid (propanonic acid), CH 3 COC0 2 H, is formed 
by the oxidation of lactic acid, CH 3 CHOHC0 2 H, by boiling 
a-dichlorpropionic acid, CH 3 CC1 2 C0 2 H, with water, by the 
saponification of acetyl cyanide, CH 3 COCN (from acetyl 
chloride and silver cyanide) with hydrochloric acid, and by 
distilling racemic or tartaric * acid, either by themselves, or 
mixed with acid potassium sulphate. 

Pyroracemic acid is a liquid which boils with some decom- 
position at 165 . It solidifies at a low temperature, and 
melts at 9 . It mixes in all proportions with water, alcohol, 
and ether. 

* Pyroracemic acid must not be confused with methyl succinic acid, 

CH 3 — CH— C0 2 H 

CH 2 — C0 2 H ' 

which is also formed by the distillation of tartaric or racemic acid, and which has, 
unfortunately, been called pyrotartaric acid. 



PYRORACEMIC ACID. 345 

When heated by itself, pyroracemic acid gives, at 170 , 

acetic acid, carbon dioxide, methyl succinic acid (pyrotar- 

taric acid), citraconic acid, 

CH 3 -C-C0 2 H 

II 
HC-C0 2 H 

and uvinic acid (dimethylfurane carboxylic acid), 

H-C C-C0 2 H 

II II 

CH3-C-O-C-CH3 

The formation of the last three acids illustrates the ten- 
dency of the acid to polymerize or condense with itself. 
It also condenses readily with many other substances. 
Thus, with benzene and concentrated sulphuric acid it 
gives diphenylpropionic acid, CH 3 C(C 6 H 5 ) 2 C0 2 H, and simi- 
lar condensation products with phenol and other aromatic 
compounds. 

Pyroracemic acid, as a ketone, gives a phenyl hydrazone, 

C 6 H 6 NHN=C<g H , 

an oxime, CH 3 C(NOH)C0 2 H, a double compound with acid 
sodium sulphite, CH 3 



OH 
, ^SOJSTa' 



C0 2 H 

and a cyanhydrin, CH 3 

c< OH 

7 < CN 



C0 2 H 



with hydrocyanic acid. 



346 ORGANIC CHEMISTRY. 

Phenylglyoxylic Acid, C 6 H 5 COC0 2 H, is prepared by the 
oxidation of acetophenone, C 6 H 5 COCH 3 , with a cold, 
strongly alkaline solution of potassium permanganate. The 
name represents it as a derivative of glyoxylic acid, HCO— 
C0 2 H. It can also be prepared from benzoyl cyanide, 
C 6 H 5 COCN. Phenylglyoxylic acid melts at 66°. It is 
easily soluble in water and ether, but insoluble in carbon 
disulphide. It decomposes, on heating, chiefly into benzoic 
acid and carbon monoxide, but partly into benz aldehyde and 
carbon dioxide. It is easily oxidized to benzoic acid by 
manganese dioxide and sulphuric acid, resembling, in this, 
oxalic acid, to which it is related. 

Phthalonic Acid, 

COC0 2 H 
^ 4< CO s H ' 

is prepared by the oxidation of naphthalene with potassium 
permanganate in an alkaline solution (p. 261). 

Formyl Acetic Acid, 

//O 



CH 2 < 



C XH, 



or /^-hydroxy acrylic acid, 

^CHOH 
\C0 2 H ' 

is not known in the free state. Its ethyl ester is formed 
by the action of sodium upon a mixture of the ethyl esters 
of formic and acetic acid, 

HC0 2 C 2 H 5 + CH 3 C0 2 C 2 H 5 + Na 

/ONa 
= H-C = CH-C0 2 C 2 H 5 +C 2 H 5 OH + H. 

Sodium salt of formyl acetic ester. 



ACETOACETIC ACID. 347 

The reaction is similar to that for the preparation of aceto- 
acetic ester, which will be discussed below. 

When the sodium salt is treated with acetyl chloride an 
acetyl derivative, 



^CHOC 2 H 3 
\ C0 2 C 2 H 5 ' 



is formed, which has been shown to be an unsaturated com- 
pound by the fact that it adds two atoms of bromine directly. 
This indicates that the sodium salt, at least, has the " enol " 
form (pp. 205 and 349). 

Fomyl acetic ester is very unstable, condensing spontane- 
ously in its solutions,, to trimesitic ester, 

/C0 2 C 2 H 5 1 
C 6 H s -C0 2 C 2 H 5 3. 
\,C0 2 C 2 H 5 5 

Acetoacetic Acid, CH 3 COCH 2 C0 2 H, 

or CH 3 C (OH) = CH - C0 2 H, 

is not known in the free state otherwise than in solution. 
It is found in the urine of persons suffering from diabetes, 
and sometimes in those suffering from fevers. Its presence 
is believed always to be pathological. 

Acetoacetic Ester. — The ethyl ester, CH 8 COCH 2 C0 2 C 2 H 5 
or CH 3 C(OH) = CH-C0 2 C 2 H 5 , is formed by the action of 
metallic sodium upon acetic ester. It is believed that the 
sodium at first acts upon a trace of alcohol present in the 
ester to form sodium ethylate, and that the latter adds itself 
to the acetic ester to form the compound, 

/ OC 2 H 5 
CH 3 -C-0C 2 H 5 . 
x ONa 



348 ORGANIC CHEMISTRY. 

This compound then condenses with another molecule of 
acetic ester thus : 

;OC 2 H 5 "H! 

!0C 2 H 5 Hi 

ONa H 



/ 

CH 3 C- 

\ 



\ 

— O — u0 2 C 2 Ht 

/ 



This reaction, and many others of a similar character 
which have a bearing upon it, have been very carefully 
studied by many different chemists ; and both the reaction 
and the structure of the acetoacetic ester have been subjects 
of much controversy. Prominent chemists still hold diver- 
gent views upon some of the questions involved. The ex- 
planation given is that of Claisen, and depends chiefly on the 
facts : 

i. That addition compounds of the character supposed 
have been prepared, as, for instance, the compound, 

/ OC 2 H 5 
C 6 H 6 C — OC 2 H 5 , 
\ONa 

from benzoic ester and sodium ethylate. 

2. That this addition compound reacts with acetic ester 
to form sodium benzoyl acetic ester, 

C 6 H 5 C = CH — C0 2 C 2 H 5 
\ONa 

3. That esters condense in this manner only when, they 
have at least two hydrogen atoms combined with the carbon 
atom adjacent to the carboxethyl ( C0 2 C 2 H 5 ) group. Thus 
oxalic ester, 

C0 2 C 2 H 5 

I 
OOoC 9 Hc 



ACETO ACETIC ACID. 349 

condenses with normal butyric ester giving the compound, 

7 0Na 
C= 

I 

C0 2 C 2 H 5 C0 2 C 2 H 5 

but it will not condense with isobutyric ester, 

^ 3 >CH-C0 2 C 2 H 5 . 
Cri 3 

Acetoacetic ester is a colorless liquid with a pleasant odor. 
It boils with slight decomposition at 180 . It gives a violet 
color with ferric chloride, recalling the color given by sali- 
cylic and other orthohydroxy aromatic acids. In cases where 
derivatives of acetoacetic acid have been prepared in both 
the ketone (R - COCH 2 C0 2 C 2 H 5 ) and " enol " 

(R - C(OH) = CHC0 2 CH 5 ) 

form, it has been found that only the latter gives the reac- 
tion with ferric chloride. This justifies the conclusion that 
the free acetoacetic "ester exists, at least in part, in the 
" enol " form.* The resemblance to phenols is further shown 
by the solubility of the ester in solutions of sodium or potas- 
sium hydroxide and its precipitation from such solutions by 
carbonic acid. 

Acetoacetic ester also gives reactions in which it behaves 
as a ketone. It forms a double compound with acid sodium 
sulphite, and decomposes into acetone, carbon dioxide, and 
alcohol when boiled with dilute acids. 

Many other reactions can be interpreted by either the ke- 
tone or enol formula. The more common opinion, at present, 

* Schiff has given some evidence which seems to show that the ester sometimes 
consists exclusively of the "enol" form. Ber. d. chem. Ges., 31, 6oi, 1388. See 
also Traube, Ibid, 29, 1715. 



350 ORGANIC CHEMISTRY. 

is that in the metallic derivatives the metal is combined with 
oxygen ; thus, that sodium acetoacetic ester is 

/ONa 



and not 



CH 3 C = CH — C0 2 C 2 H 5 



CH 3 CO - CHNaC0 2 C 2 H 5 , 



though the latter formula is still used, often, perhaps, with- 
out intending to express an opinion as to the real structure. 
(For the effect of solvents on tautomeric compounds see 
Bamberger, Ber. d. chem. Ges. 34, 2003.) It has been found 
that in the presence of water or alcohol the transformation 
from the ketone to the enol form, or vice versa, takes place 
much more easily than in the presence of ligroin, chloroform, 
or benzene. 

Condensations with Acetoacetic Ester. — When the metallic 
derivatives of acetoacetic ester are treated with halogen com- 
pounds, derivatives are obtained in which the radical some- 
times unites with carbon and in other cases with oxygen. 
As types of the two classes of reactions may be given the 
following : 

/ONa 
CH 3 C = CH-C0 2 C 2 H 5 +C 2 H 5 I 

/ ONa / C 2 H 5 

= CH 3 -CI CH-C0 2 C 2 H 5 

/C 2 H 5 
= CH 3 COCH-C0 2 C 2 H 5 + NaI. 

Ethyl acetoacetic ester. 

/ Ocu* 
CH 3 -C = CH-C0 2 C 2 H 5 + CH 3 C0C1 

/ OC 2 H 3 
= CH 3 -C= CHC0 2 C 2 H 5 +cuCl 

O-acetyl-acetoacetic ester. 
* By cu is meant the half atom of copper. 



KETONIC DECOMPOSITION. 35 I 

Reactions of the second type are interesting as furnishing 
evidence of the structure of the salts of acetoacetic ester, but 
those of the first type are of much greater practical im- 
portance. By means of similar reactions compounds of the 
general formula CH 3 COCHRC0 2 C 2 H 5 and 

CH 3 COCRR'C0 2 C 2 H 5 
have been prepared in very great variety. The synthesis 
is similar to the malonic ester synthesis (p. 252), and by 
means of the " acid decomposition " it may lead to the same 
products. It is worthy of notice that when both hydrogen 
atoms of the methylene (CH 2 ) group have been replaced, 
the product is no longer soluble in alkalies, because it is 
necessarily of the "ketone form." 

Acid Decomposition. — Boiling with alkalies or acids sa- 
ponifies acetoacetic ester, or its derivatives, but the resulting 
acids are unstable and usually undergo a further decomposi- 
tion. In alkaline solutions, in general, though by no means 
always, the acid undergoes the " acid decomposition," losing 
the acetyl group, and giving acetic acid or a derivative of 
acetic acid : 

CH 3 -CO j CH-C0 2 C 9 H 5 + 2NaOH 
\C 2 H 5 

= CH 3 C0 2 Na + C 2 H 5 OH + H 2 + C 2 H 5 Cli 2 C0 2 Na. 

Sodium butyrate. 

Ketonic Decomposition. — The acid decomposition gives 
the same product which would be obtained by the decompo- 
sition of the bibasic acid resulting from the malonic ester 
synthesis (p. 252); and, in general, malonic ester or cyana- 
cetic ester is to be preferred for syntheses of this kind. 

When boiled with acids, usually with hydrochloric or sul- 
phuric acid, acetoacetic ester and its derivatives undergo 
"ketonic decomposition," and give a ketone : 



352 ORGANIC CHEMISTRY. 

CH 8 -C0CH-UC0 2 C 2 H 6 + HC1 + H 2 = C0 2 +C 2 H 5 OH 

I : 
C 2 H 5 + C 2 H 5 CH 2 COCH 3 

Propyl methyl ketone. 

In some cases, when a clean " acid decomposition " can- 
not be secured, and the substance s'ought is the acid and 
not the ketone, the latter may be oxidized to the acid by 
means of sodium hypochlorite or hypobromite (p. 199) : 

C 2 H 5 CH 2 -COCH 3 + 3NaBrO = 

C 2 H 5 CH 2 C0 2 Na4-CHBr 3 +2 NaOH. 

A considerable number of synthetic processes closely 
analogous to that of the preparation of acetoacetic ester are 
known. Among the most interesting of these are several 
which give rise to cyclic compounds. As has been noticed 
so often in other cases, only those reactions which result in 
rings of five or six carbon atoms take place readily and 
with satisfactory yields. 

Carboxethyl Cyclopentanone, 

CH, — CH 9 



> CHC0 2 C 2 H 5 . 



CH 9 -CO 



u 2 

When sodium, in the form of wire, is introduced into a 
mixture of adipic ester and toluene, and the mixture is 
heated, condensation to a cyclic compound takes place : 

CH 2 CH 2 - CH„- C0 2 C 2 H 5 

I +Na 

CH 2 — C0 2 C 2 H 5 

= f H2 " CH2 )C-C0 2 C 2 H 5 

CH 2 C — ONa + C 2 H 5 OH + H. 



CARBOXETHYL CYCLOPENTANONE. 353 

The free carboxethyl cyclopentanone is obtained from the 
sodium salt on the addition of dilute sulphuric acid. It 
boils with slight decomposition at 220 , or at no° under a 
pressure of 15 mm. The sodium salt is quite difficultly 
soluble in water. /The copper salt is also difficultly soluble, 
even in the presence of some acetic acid. This indicates 
the decided acid character of the ester, and that it exists, 
largely at least, in the " enol " form. 

When the ester is saponified with alkalies, adipic acid is 
regenerated (acid decomposition). When boiled with acids, 
it is decomposed into carbon dioxide and cyclopentanone, 

CH 2 — CH 2 

1 >co, 

CH 2 — CH 2 

(ketonic decomposition). 

When the sodium salt of the ester is treated with methyl 
iodide , 2 -methyl-2 -carboxethyl-cydope?ita?wne, 

CH 2 — ^H 2 ^-H-3 

I >C< 

CH 2 -CO C0 2 C 2 H 5 , 

is formed ; and this gives, by saponification, a-methyladipic 
acid. The ethyl ester of the latter may be condensed, in 
the same manner as the adipic ester, to ^-methyl-2-carbox- 
ethyl cyclopentanone, 

CH 2 — CH — ^Hs 

I >co 

CH 2 -CH-C0 2 C 2 H 5 . 

The hydrogen adjacent to the carboxethyl group in this 
compound may also be replaced by methyl. These facts 
illustrate some of the syntheses which may be effected with 
compounds of this character. 



354 ORGANIC CHEMISTRY. 

Carboxethyl Cyclohexanone and its derivatives can be ob- 
tained from pimelic ester, 

CH CH 2 -C0 2 C 2 H 5 

I 
CH 2 CH 2 -CH 2 C0 2 C 2 H 5 

in a similar manner. 

Succinylosuccinic Ester, 

C0 2 CH 5 C0 2 C 2 H 5 

I I 

C CH 

/ ^ / \ 

CH 2 COH CH 2 CO 

I I , or | | , 

COH CH 2 CO CH 2 

^ / \ / 

C CH 

I I 

C0 2 C 2 H 5 C0 2 C 2 H 5 

is formed as a sodium salt when sodium wire and a few 
drops of alcohol are allowed to act on succinic ester, 

CH 2 — C0 2 C 2 H 5 

I 

CH 2 — C0 2 C 2 H 5 

In this case two molecules of the ester condense together. 

Succinylosuccinic ester crystallizes in yellowish or greenish 

leaflets, which melt at 127 . It dissolves readily in alkalies, 

and gives, with ferric chloride, an onion red color, indicating 

that it exists in the enol form. 

When boiled with dilute sulphuric acid it gives 1.4 cyclo- 

hexanedion, CH 9 -CH 2 -CO 

I I , 

CO- CH 2 -CH 2 

by ketonic decomposition. 



levulinic acid. 355 

When treated with bromine, it is converted quantitatively 
into dioxyterephthalic ester, 

C0 2 C 2 H 5 i 

X OH 5 

This conversion is of especial interest, as it disproves the 
Ladenburg formula for benzene (p. 101). (Baeyer, Ber. 
der chem. Ges. 19, 1798.) 

Levulinic Acid (4-pentanonic acid), 

CH 3 COCH 2 CH 2 C0 2 H, 

is the simplest and best-known y-ketonic acid. It is pre- 
pared by heating starch, levulose, cane sugar, and some other 
carbohydrates with dilute hydrochloric acid: 

C 6 H 12 6 = C 5 H 8 3 +HC0 2 H + H 2 0, 



Levulose. Levulinic acid. Formic acid. 


CH 2 OH 




1 


CH 3 


CO 


1 


1 


CO 


CHOH 


1 


1 


= CH 2 +H 2 C0 2 +H 2 


CHOH 


1 


1 


CH 2 


CHOH 


1 


1 


C0 2 H 


CH 2 OH 





The reaction is accomplished by an internal reduction and 
oxidation, which is suggestive, but which is very little under- 
stood. The reaction is accompanied by others which cause 
the complete decomposition of a large part of the sugar ; and 
the yield is small, only ten or fifteen per cent of the weight 
of sugar used. 



356 ORGANIC CHEMISTRY. 

Levulinic acid melts at 33 , boils with but slight decom- 
position at 239 , and with no decomposition at 149 under 
a pressure of 15 mm. The difference in stability between 
the /?- and y-ketonic acids is very noticeable and remarkable. 

When levulinic acid is kept for some time at its boiling 
point, it is gradually converted into two isomeric anhydrides, 
called angelicalactones. The a-anhydride, 

CH 3 — C = CH — CH 2 , 

I I 

O CO 

boils at 167 ; the /3-anhydride, 

CH 2 == C — CH 2 CH 2 
I I , 

O CO 

at 208 . The a-anhydride solidifies at a low temperature, and 
melts at 18 . Each anhydride unites directly with two atoms 
of bromine, the /^-anhydride combining with the bromine less 
readily than the a-anhydride. 

Laboratory Exercises. 
Preparation of the following: 

1. Acetoacetic ester. 

2. Phenylglyoxylic acid. 

3. Phthalonic acid. 

4. Condensation of acetoacetic ester with benzyl chloride and 
preparation of hydrocinnamic acid. 

5. Succinylosuccinic ester. 

6. Levulinic acid. 



CARBOHYDRATES. GLUCOSIDES. 



357 



CHAPTER XVII. 

CARBOHYDRATES. GLUCOSIDES. 

The specific rotations given below are for a io°f aqueous 
solution of the anhydrous sugar with sodium light. 





Pentoses. 


C 5 H J() 5 . 






Wd. 






l-Arabinose 


-S3 






d-Arabinose 


+105-1° 






i-Arabinose 


o 






d-Xylose 


+ i8.8° 






1-Xylose 


— 18.05 








Hexoses. 


C 6 H 12 6 . 




A-Aldohexoses. 




Reduction 
Product. 


Oxidation 
Product. 


d-Glucose 


52-7° 


d-Sorbite 


d-Saccharic acid. 


1-Glucose 


- 5i-4° 





1-Saccharic acid. 


i-Glucose 








i-Saccharic acid. 


d-Gulose 








d-Saccharic acid. 


1-Gulose 





1-Sorbite 


1-Saccharic acid. 


i-Gulose 








i-Saccharic acid. 


d-Galactose 


+ 81.5 


Dulcite 


Mucic acid. 


[-Galactose 


- 73-6° 


Dulcite 


Mucic acid. 


i-Galactose 








Mucic acid. 


d-Mannose 


+ U.25 


d-Mannite 


d-Mannosaccharic acid. 


1-Mannose 





1-Mannite 


1-Mannosaccharic acid. 


i-Mannose 





i-Mannite 


i-Mannosaccharic acid. 


B-Ketohexoses. 








d-Fructose 





( Mannite and 
I Sorbite 




1-Fructose (levulose) 


- 93 -° 




i-Fructose (a-acrose) 





i-Mannite 




1-Sorbinose 





Sorbite 




i-Inosite (hexahydroxy) 

cyclohexane) 
Rhamnose (Ci 2 H 10 O 5 ) 




+ 8-4° 







358 ORGANIC CHEMISTRY. 

Heptoses, C 7 H u O r 

Rhamnohexose, a-Glucoheptose, /3-Glucoheptose, 
d-Mannoheptose, 1-Mannoheptose, i-Mannoheptose, 

Octoses, C 8 H 16 8 . 

Rhamnoheptose, a-Glucose, d-Mannooctose. 

Nonoses, C 9 H l8 9 . 

Glucononose, Mannononose. 

DlSACCHARIDES, C 12 H 22 O n . 





Hi?. 






Products of 








Hydrolysis. 


Maltose 


+ 137-04° 






Glucose. 


Isomaltose 


+ 6 9 .°(?) 






Glucose. 


Melibiose 


+ 129.38° 






Glucose, galactose. 


Lactose (Milk sugar) 


52-5° 






Glucose, galactose. 


Saccharose (Cane Sugar) 


+ 66.54° 




Glucose, fructose. 


Trehalose 


+ 199° 






Glucose. 


Turanose 









Glucose. 


Trisaccharides, 


^18 ■"•32 ^16' 




Raffinose (Melitose, 


104.5 






Glucose, turanose. 


Melitriose) 










Melezitose 


88.5° 






Fructose, melibiose. 


f Amylodextrin 

_ . Acrobdextrin 
Dextrin < _ - , . 
Erytnrodextnn 


193-4° 








192.° 






Glucose. 


196.° 








[_ Maltodextrin 


i8i°-i8 3 ° 








Inulin 


- 36.57° 






Fructose. 


Arabin 


- 98-5° 






Arabinose. 


Xylan 


- 84.° 






Xylose. 


Lactosin 


+ 2II. 7 ° 






Galactose and (?) 


a-Amylan 


a)= — 24° 






Glucose. 


/3-Amylan 


*j = - 73° 






Glucose (?). 


Starch 


+ 






Glucose. 


Cellulose 


-(?) 






Glucose. 



The name " carbohydrate " has been given to a class of 
bodies, mostly of vegetable origin, which contain carbon, 
hydrogen, and oxygen, and in which the proportion between 
the hydrogen and oxygen is the same as in water. The 



TETROSE. 359 

group includes starch and sugar, the most important non- 
nitrogenous compounds in the food of men, and cellulose, an 
important article of diet for herbivorous animals. 

A very large proportion of the natural carbohydrates have 
molecules containing six, or a multiple of six, carbon atoms. 
Some natural gums are known, however, which have in their 
molecules a multiple of five carbon atoms ; and these yield, 
by hydrolysis, sugars with molecules containing but five car- 
bon atoms. Sugars containing larger and smaller numbers 
of carbon atoms have been prepared synthetically. 

In composition, formaldehyde, CH 2 0, might, in some 
sense, be considered as the simplest carbohydrate, but has 
few of the properties characteristic of the carbohydrates, and 
is never classed with them. The theory that formaldehyde 
is the first reduction product of carbonic acid in plants, and 
that starch is formed by its polymerization (Baeyer Ber. 
d. chem. Ges. 3, 63) has, however, much in its favor. 

Tetrose, CH 2 OH 

I 
CHOH 

I 
CHOH 

I>0 

\H 

may, perhaps, be considered as the simplest sugar, though 
glycol aldehyde, 

CH 2 OH 

I 
CHO 

and glycerol aldehyde, 

CH 2 OH,CHOH,CHO, 
might, from the definition, be termed carbohydrates and 



360 ORGANIC CHEMISTRY. 

called diose and triose. Tetrose is formed by the polymeriza- 
tion of glycol aldehyde, when its solution, containing one 
per cent of sodium hydroxide, is allowed to stand at o° for 
fifteen hours. 

Arabinose and Xylose, 

CH 2 OH 

I. 

CHOH 

I 
CHOH, 

I 
CHOH 

I /H 

have the same structure, but different configurations, and, so, 
different rotatory power, and different properties in other 
respects. Each gives furfural, 

CH-C-CHO 

I >o, 

CH = CH 

when heated with dilute hydrochloric or sulphuric acid. 
This indicates, very clearly, the structure of the sugars. 
The reaction is closely analogous to the formation of dehy- 
dromucic acid from saccharic and mucic acids (p. 339). As 
furfural can be readily determined quantitatively, its forma- 
tion is made the basis for the determination of xylose and 
of xylan, which yields xylose by hydrolysis with dilute acids. 
Both arabinose and xylose reduce Fehling's solution. 
Neither arabinose nor xylose can be fermented with pure 
yeast. Bacillus e?ithaceticus, however, causes the fermenta- 
tion of arabinose with formation of hydrogen, carbon diox- 
ide, ethyl alcohol, and acetic acid. 



D-GLUCOSE. 361 



^/-Glucose (Grape sugar, dextrose, starch sugar), 

CH 2 OH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

I 
CHOH 

£'° 

\H 

is the most important of the hexoses, or sugars containing six 
carbon atoms in the molecule. Glucose is found widely 
disseminated in the vegetable kingdom, usually associated 
with an equivalent amount of fructose. Starch, dextrin, 
and maltose are converted, almost quantitatively, into glu- 
cose by the hydrolysis effected by heating with dilute acids. 
It is also a partial product of the hydrolysis of cane sugar, 
milk sugar, raffinose, and several other disaccharides and 
polysaccharides. Glucose is secreted in the urine in the 
disease known as diabetes melitus^ sometimes in very consid- 
erable quantities. 

Glucose is most easily prepared pure from cane sugar, 
which is very easily hydrolysed by the action of dilute acids, 
yielding glucose and fructose in equivalent amounts. From 
the mixture, glucose crystallizes more easily than fructose, 
and can be obtained pure without much difficulty. 

Commercially, glucose is manufactured in large quantities 
from starch. Commercial glucose usually contains consid- 
erable amounts of maltose, dextrin, and other substances. 

Glucose crystallizes from water in microscopic, six-sided 
tablets which contain one molecule of water. It crystallizes 



362 ORGANIC CHEMISTRY. 

from absolute alcohol in needles which are free from water. 
It is optically active. [a] D = + 52.7 for a ten per cent 
aqueous solution. The value increases slightly with increas- 
ing concentration of the solution. A cold, freshly prepared 
solution gives a rotation which is much higher ; but after 
standing for some time, or after boiling for a few minutes, 
the rotation falls to the normal value. This phenomenon is 
called " birotation " or " multirotation," and, if not taken into 
account, is liable to cause serious error in working with 
some of the sugars. 

Pure glucose is only about one-half as sweet as cane sugar. 
Commercial glucose is still less sweet. 

Structure of Glucose. — The view held of the structure of 
glucose depends on the following facts : 

1. It gives by reduction with sodium amalgam manntte, 
C 6 H 14 6 , and this, by reduction with hydriodic acid, gives 
secondary hexyl iodide, CH 3 CHICH 2 CH 2 CH 2 CH 3 , proving 
the presence of a normal chain of carbon atoms. 

2. It gives, when heated with acetic anhydride and zinc 
chloride, a pentacetate, C 6 H 7 12 (C 2 H 3 0) 5 , demonstrating the 
presence of five hydroxyl groups. 

3. It combines with hydrocyanic acid to form a cyan- 
hydrin, 

CH 2 OH 

I 
(CHOH) 4 , 

CH<£H 

which can be saponified to a-glucoheptonic acid, CH 2 OH 
(CHOH) 5 C0 2 H. The lactone-anhydride of this acid is re- 
duced to normal heptylic acid, CH 3 (CH 2 ) 5 C0 2 H, by heating 



SYNTHESIS OF GLUCOSE. 363 

with hydriodic acid. This proves that the hydrocyanic acid 
must have combined with the end carbon atom, and that 
glucose contains an aldehyde and not a ketone group. 

Synthesis of Glucose. — ^/-Glucose has been prepared, syn- 
thetically, by the following series of reactions. Glycerol, by 
oxidation with bromine and sodium carbonate, gives glycerol- 
aldehyde, CH 2 OH,CHOH,CHO. When this is allowed to 
stand for four or five days in an aqueous solution containing 
one per cent of sodium hydroxide, it polymerizes to a sugar 
which was called at first a-acrose, but which has been shown 
to be /-fructose, 

CH 2 OH,CHOH,CHOH,CHOHCOCH 2 OH. 
This is reduced by sodium amalgam to i-mannite, 

GH,OH(CHOH) 4 CH,OH, 
and this, in turn, can be oxidized to z'-mannose, 

CH 2 OH(CHOH) 4 CHO ; 
and z-mannonic acid, 

CH 2 OH (CHOH) 4 C0 2 H. 

The z'-mannonic acid can be separated into its active com- 
ponents by means of the strychnine salt. The ^/-mannonic 
acid, when heated with pyridine, is partly converted into 
^/-gluconic acid, which has the same structural arrangement 
but a different configuration. Finally ^/-gluconic acid gives 
^/-glucose by reduction. 

A hot solution of glucose reduces a hot Fehling's solution,* 
and this reaction can be used both for its detection and 

* Fehling's solution, which is much used in work with sugars, is best kept in the 
form of two separate solutions, the first containing, in 500 cc, 173 grams of Rochelle 
salt and 50 grams of sodium hydroxide ; the second containing, in 500 cc, 34.639 grams 
of crystallized copper sulphate. For use, equal volumes of the two solutions are 
mixed. 



364 ORGANIC CHEMISTRY. 

quantitative determination, when other reducing substances 
are absent. 

Glucosazone. — When a solution containing glucose is 
warmed with phenyl hydrazine acetate, glucosazone, 

CH 2 OH 

I 
(CHOH) 3 

I 
C = N-NHC 6 H 5 

I 

CH = N-NHC 6 H 5 

is formed. The phenyl hydrazine combines at first with the 
glucose to form a phenyl hydrazone, a second portion of the 
hydrazine then oxidizes the adjacent CHOH group, and 
finally, more of the phenyl hydrazine reacts with the ketone 
group which is produced. Many other sugars react in a 
similar manner to form osazones, and the resulting com- 
pounds have been extremely useful for the separation and 
identification of different sugars. Glucosazone crystallizes 
in yellow needles, which melt, when quickly heated, at 206 . 

^/-Glucose ferments easily under the influence of brewer's 
yeast, giving chiefly alcohol and carbon dioxide (p. 130). 
I- Glucose, on the contrary, does not ferment with brewer's 
yeast, and one-half of /-glucose, only, is fermented by the 
same agency. E. Fischer has suggested that some relation 
similar to that of a key to its lock must exist, in such 
cases, between the compounds of the organism and the 
fermentable body. 

/-Glucose was prepared by the reduction of l-gluconic 
anhydride (see above), and /-glucose by the reduction of 
/-gluconic anhvdride. Neither has been found in nature. 



L-FRUCTOSE. 365 

1-Fructose (levulose, fruit sugar), 
CH 2 OH 

I 
(CHOH) 3 , 

I 
CO 

I 
CH 2 OH 

is found accompanying //-glucose in most sweet fruits, and is 
very widely distributed in nature. It is formed in equal 
amount with //-glucose by the hydrolysis of cane-sugar, the 
mixture of the two being called " invert sugar." 

Fructose forms a pentacetyl derivative. It is reduced 
to a mixture of mannite and sorbite by sodium amalgam. 
It combines with hydrocyanic acid to form a cyanhydrin. 
The acid obtained by saponifying the cyanhydrin is reduced 
to methyl butyl acetic acid, 

CH 3 CH 2 CH 2 CH 2 — CH — C0 2 H, 

I 
CH 3 

on heating with hydriodic acid. Fructose gives with phenyl 

hydrazine, an osazone identical with that obtained from 

glucose. By oxidation with nitric acid it gives glycollic acid, 

CH 2 OH 

I 
C0 2 H 

and inactive tartaric acid, 

CHOH-C0 2 H 

I 

CHOH-C0 2 H 

These facts establish its structure. 

/- ( Fructose reduces Fehling's solution, and may be deter- 
mined quantitatively in that manner. /-Fructose undergoes 



366 ORGANIC CHEMISTRY. 

fermentation with brewer's yeast ; //-fructose ferments still 
more easily, so that it is possible, by partial fermentation, to 
obtain the /-fructose from the /-fructose (a-acrose) prepared 
by synthesis. 

A considerable number of other sugars of the same struc- 
ture as glucose, and a few of the same structure as fructose, 
but differing from them in configuration and properties, are 
known. These are distinguished by formulae, of which the 
following are illustrations : 

CHO CHO 

I I 

H-C-OH HO-C-H 

I I 

HO-C-H HO-C-H 

I I 

H-C-OH H-C-OH 

I I 

H-C-OH HO-C-H 

I I 

CH 2 OH CH 2 OH 

d-Glucose. d-Gulose. 

By placing the hydroxyl group to the right or left of a 
given carbon atom, it is intended to indicate whether that 
carbon atom produces a right-handed or left-handed rotation. 
A study of the possible combinations shows that there may 
be sixteen different configurations for a substance of the 
structure of glucose. Eleven such substances are now 
known, and five racemic forms resulting from the combina- 
tion of forms which are optically opposite. By means of 
a careful study of the relations between the different forms, 
of their relations to mannite and sorbite, to saccharic and 
mucic acids, and to active tartaric acid, Emil Fischer has 
determined the configuration of glucose and of several other 
aldohexoses with a good degree of certainty. This must be 



SACCHAROSE. . 367 

considered as the most difficult problem thus far solved in 
the study of space-isomerism. 

Inosite (hexoxyhexahydrobenzene, or hexahydroxycyclo- 
hexane), C 6 H 6 (OH) & -J-2H 2 0, is found in the lungs, kidneys, 
liver, and brains of oxen, sometimes in the urine, and in a 
variety of fruits and vegetables. It does not reduce Fehl- 
ing's solution. Nitric acid oxidizes inosite to tetroxyquinone, 
C 6 H 4 6 ; hydriodic acid, at 170 , reduces it to phenol, triiodo- 
phenol, and a trace of benzene. 

Although isomeric with the other hexoses, inosite is radi- 
cally different from them in structure and properties. 

Sugars containing seven, eight, and nine carbon atoms in 
a molecule have been prepared synthetically, but none of 
them have been found in natural products. 

DlSACCHARIDES, C 12 H 22 O u . 

Saccharose (cane-sugar), C 12 H 22 O n , is very much the most 
important of all the sugars. It is prepared commercially 
from sugar-cane, beets, sorghum, and the sap of maple- 
trees, and is found in a very great variety of plants and 
vegetables. 

In the manufacture of sugar from the sugar-beet, the 
material is first cut into very small, thin pieces. These are 
then subjected to the action of water in a " diffusion battery " 
of ten or twelve large iron cylinders, so arranged that the 
water may enter at any one of the cells desired, and circulate 
in order through the others. In contact with water, the 
amount of sugar in the beet-chips, and in the water sur- 
rounding them, is quickly equalized by diffusion. By so 
arranging the current of water that it enters the battery 
at the cell where the chips are most nearly exhausted, 
and leaves at the cell which has been last filled, it is pos- 



368 ORGANIC CHEMISTRY. 

sible, both to secure a very complete removal of the sugar, 
and also to obtain a solution with a content of sugar ap- 
proaching very nearly to that of the original beet-juice. 

The sugar-cane is sometimes treated by the diffusion 
process, but more usually the sap is expressed from the 
cane by means of heavy iron or steel rollers. A very much 
smaller per cent of sugar (about 70 per cent) is recovered 
by the rolls than by diffusion (about 84 per cent) ; but the 
residue can be used as fuel in the former case, and this 
is usually an important item in the localities where sugar-cane 
is chiefly grown. The exhausted beet-chips, on the other 
hand, are often used as a cattle food. 

The juice or solution is next treated with milk of lime or 
powdered lime, and warmed to precipitate phosphoric acid, 
oxalic acid, citric acid, albuminous bodies, and other impuri- 
ties. The clear solution, after their removal, is treated with 
carbon dioxide, and sometimes with sulphur dioxide, to re- 
move the excess of lime. As even a trace of acid causes 
some " inversion " and loss of sugar, it is important that the 
solution shall always remain faintly alkaline. 

The solution is then evaporated in vacuum pans, the syrup 
cooled and allowed to crystallize, and the " molasses " sep- 
arated from the crystals by means of centrifugals. The 
crude sugar is usually further purified in sugar refineries by 
solution, filtering through boneblack, and recrystallizing. 

The "molasses," especially that from cane-sugar, is often 
sold as such ; that from beet-sugar is usually fermented for 
the manufacture of alcohol ; and the spent liquors, after dis- 
tillation, are evaporated and calcined, partly for the manu- 
facture of methyl alcohol and other products, partly for the 
recovery of potassium salts and other inorganic compounds 
of value as fertilizers. 

Pure cane sugar, whether from the sugar-cane or beets, is 



SACCHAROSE. 369 

without effect on Fehling's solution. It is optically active, 
\a~\ D = +66.5 1 4 at 20 for a solution containing 26.004 
grams of sugar in a volume of 100 cc, the value varying 
slightly with the temperature and concentration (Wiley, J. 
Am. Ch. Soc. 21, 594). When heated for a short time with 
dilute hydrochloric acid, it is hydrolyzed, giving a mixture of 
^/-glucose and /-fructose, which is known as " invert " sugar, 
since the fructose causes a greater rotation to the left than 
glucose does to the right. Since most impure commercial 
sugars contain a mixture of cane sugar and invert sugar, a 
determination of the rotatory power before and after inver- 
sion furnishes the necessary data for calculating the per 
cent of each which is present. Such determinations are 
made the basis for the collection of duty to the amount of 
millions of dollars annually at our ports of entry. 

Came sugar does not ferment directly, but it is easily in- 
verted by an enzyme which always accompanies ordinary 
yeast, and both the glucose and fructose then undergo fer- 
mentation. 

Cane sugar crystallizes in monoclinic prisms. It melts at 
160 . At temperatures below 20 it is soluble in one-half its 
weight of water. At 50 it dissolves in a little less than one- 
fourth of its weight of water. 

Cane sugar, as well as other sugars, forms, with bases, 
compounds called saccharates, of which those with cal- 
cium, strontium and barium are most important. Those of 
the cane sugar with calcium are C 12 H 22 O n • CaO + 2H 2 0, 
C^H^On • 2CaO, and C^H^On * 3CaO. The first is easily 
soluble, the second dissolves in -^Z parts of cold water, the 
third in 200 parts of cold water. 

Cane sugar also forms double compounds with sodium chlo- 
ride and with other salts, as, for example, C 12 H 22 O n . NaCl. 

The exact structure of cane sugar has not been fully 



370 ORGANIC CHEMISTRY. 

established. It forms no compound with phenyl hydrazine, 
and hence probably contains no aldehyde or ketone group, 
a fact which also explains its failure to react with Fehling's 
solution. It forms an octacetate, C 12 H 14 O u (C 2 H 8 0) 8 , indi- 
cating the presence of eight hydroxyl groups. The ease with 
which it is hydrolyzed by acids indicates that the radicals of 
glucose and fructose, which it must contain, are united by 
oxygen. The following formula agrees with these facts, and 
is the most probable of those which have been proposed : 

CH 2 OH 
CH 2 OH— CHOH-CH-CHOH'CHOH— CH— O— C— CHOH-CHOH'-CH— CH.OH. 

I o o I 

Lactose (milk sugar), C 12 H 22 O n 4-H 2 0, is found in milk, 
and is prepared from the whey which remains after separat- 
ing the casein in making cheese. It is much less easily 
soluble in water than cane sugar, a saturated solution at io° 
containing only 14.55 P er cen ^ °^ lactose. 

[a] Z } = 52.5°. The anhydrous milk-sugar, when first dis- 
solved, gives a smaller rotation, gradually increasing to the 
normal value. The crystallized sugar, on the other hand, 
gives a larger rotation at first. Either solution gives the 
normal value after warming. (See p. 362.) 

Lactose reduces Fehling's solution and may be determined 
in that way, but the amount of cuprous oxide precipitated is 
less than that from the same weight of glucose or fructose. 
Lactose is hydrolyzed by dilute acids to glucose and galac- 
tose. It is neither hydrolyzed nor fermented by ordinary 
yeast, but may be fermented by schizomycetes, giving alcohol 
and lactic acid. 

Maltose, C 12 H 22 O n + H 2 0, is formed, together with dextrin, 
by the action of the diastase of malt upon starch (p. 130). 
It is easily soluble in water. [a]/?= + 137.04 for the anhy- 



RAFFINOSE. 37 1 

drous maltose. The rotation of a freshly prepared solution is 
less. Maltose reduces Fehling's solution, the ratio of mal- 
tose to cuprous oxide formed being greater than for lactose. 
Maltose gives only glucose by hydrolysis with acids. The 
hydrolysis takes place with much greater difficulty than in 
the case of cane sugar. Maltose ferments directly with 
brewer's yeast, giving chiefly alcohol. Both lactose and 
maltose give compounds with phenyl hydrazine, indicating 
the presence of an aldehyde group. 

Trisaccharides, C 18 H 32 1( .. 

Raffinose (melitose, melitriose), C 18 H 32 16 +5H 2 0, is found 
in the molasses from the preparation of beet sugar, in cotton- 
seed, and in several other substances of vegetable origin. It 
is dextro-rotatory, [a] D — 104.5 . ^ d° es n °t reduce Fehling's 
solution. It is hydrolyzed by acids at first to glucose and 
melibiose ; and the latter gives, by further hydrolysis, glucose 
and galactose. It is partially fermented by yeast. Raffinose 
occasionally crystallizes with cane sugar in peculiar, pointed 
crystals. These will, of course, give a higher rotation than 
pure cane sugar. 



If the natural carbohydrates are arranged in the order of 
complexity, cellulose and starch would stand at one end, as 
having the highest molecular weights, while glucose and 
xylose would stand at the other. 

Cellulose, (QH^O^, forms the chief constituent of the 
woody fiber of plants. If cotton-wool is treated with ether, 
alcohol, sodium hydroxide, dilute hydrochloric acid, and 
hydrofluoric acid, and thoroughly washed, the residue is 
nearly pure cellulose. The best grades of washed filter- 
papers are practically pure cellulose. 



372 ORGANIC CHEMISTRY. 

Cellulose is insoluble in all of the ordinary solvents. If, 
however, a solution containing copper sulphate and ammo- 
nium chloride is precipitated with sodium hydroxide, the pre- 
cipitate thoroughly washed, and then dissolved in ammonia, 
a solution is obtained, called " Schweitzer's reagent," in 
which cellulose is soluble. The cellulose is reprecipitated 
by acids or salts. 

If cellulose is dissolved in concentrated sulphuric acid, 
and the solution is diluted and boiled, it is partly converted 
into dextrin and glucose. 

Paper consists mainly of cellulose. The best grades are 
manufactured from flax or from linen rags, cheaper kinds 
from cotton rags, wood, straw, and vegetable fibers of other 
sorts. Whatever material is used is at first disintegrated by 
boiling with sodium hydroxide or lime, and by mechanical 
means, to secure a uniform pulp. Bleaching agents are also 
often used. The pulp is then evenly distributed on a wire 
screen, passed through rolls, and dried. 

When unsized paper is dipped in strong sulphuric acid for 
a moment, and then washed with water and ammonia, it is 
superficially changed, and is converted into tough parchment 
paper, which may be used as a substitute for real parchment 
and for other purposes. 

Gun-cotton, Nitrocellulose, Pyroxylin. — When cotton wool 
is treated with a mixture of concentrated sulphuric and nitric 
acids, it is converted into esters of nitric acid which have 
been erroneously called nitrocellulose* A more correct name 
is cellulose nitrate. According to the strength of the acid, 
the character of the fiber, and the length of treatment, these 
may vary from the di?iitrate, C 12 H 18 (N0 3 ) 2 8 , to the hexa- 
nitrate, C 12 H 14 (N0 3 ) 6 4 . The lower forms are soluble in 

* For the nature of true nitro compounds see p. 411. 



STARCH. 373 

ether, amyl acetate, camphor, and other solvents. The 
solution in ether and alcohol is called collodion solution. 
The solution in amyl acetate is much used for lacquers, 
and the solution in camphor is celluloid. 

The higher nitrated cotton is the explosive known as gun- 
cotton. The pure hexanitrate is the basis of one of the 
best of the smokeless powders, indurite (Munroe, J. Am. 
Chem. Soc, 18, 833). 

Starch (amylum), (C 6 H 10 O 5 ) a ., is very widely disseminated 
in the vegetable kingdom, and forms a large percentage of 
the weight of corn, wheat, rye, barley, oats, rice, and 
potatoes. In its natural condition, starch is found in an 
organized form as starch granules, which differ from each 
other so markedly that the source from which a given sample 
of starch is derived can usually be determined by a micro- 
scopic examination. 

In manufacturing starch from corn, the grain is at first 
softened with water, then ground, and the wet material is 
allowed to ferment, which softens the gluten, and renders the 
washing away of the starch granules easier. After a time 
the material is agitated in a current of water, which carries 
off the starch in a sort of emulsion. From this it is allowed 
to settle, the water is removed as far as possible by centrif- 
ugals, and the residue dried, at first at a low temperature to 
prevent coagulation. The finished starch retains from 12 
to 18 per cent of water. 

Ordinary starch is insoluble in water. If boiled with 
water, the cell walls are ruptured, and the starch gelatinizes. 
With a considerable quantity of water, an emulsion is 
obtained which passes readily through filter paper, but it 
is doubtful if this is a true solution. Starch gives a blue 
color with an iodine solution containing potassium iodide or 



374 ORGANIC CHEMISTRY. 

hydriodic acid. Starch is converted by diastase into maltose 
and dextrin, the proportion between the two varying some- 
what with the conditions of treatment. Since maltose con- 
tains twelve atoms of carbon in the molecule, and some 
forms of dextrin at least thirty-six atoms of carbon, it is 
supposed that the molecule of starch is very complex. 

Starch is converted into dextrin, by heat. It' is converted 
successively into dextrin, maltose, and glucose by heating 
with dilute acids. (For rate of conversion see Rolfe and 
Defren, /. Am. Chem. Soc. 18, 869.) 

Dextrin is intermediate between starch and maltose or 
glucose. Commercial dextrin is prepared by heating starch 
for some time at 2oo°-2io°, or by moistening it with nitric 
acid and heating at a lower temperature. Other forms of 
dextrin can be prepared by the action of dilute acids or of 
diastase on starch. Several different kinds of dextrin have 
been isolated. The forms most certainly characterized 
have the formula, C 36 H 62 31 . All forms are easily soluble in 
water, but are insoluble in strong alcohol. 

All forms of dextrin are strongly dextro-rotatory, the rota- 
tion for the ordinary forms being about [0]^= + 196 . The 
various forms vary from [a] fl =i82°, to [^^=196°. 

Dextrin gives with iodine a violet or red color. It is 
converted into glucose by boiling with dilute acids. It is 
used as a gum, especially for the backs of postage stamps, 
gummed labels, etc. 

Dextrin does not ferment with yeast. 

Glycogen is a body somewhat resembling dextrin. It is 
found in the liver of men and of herbivorous animals. 
Dilute acids convert it into glucose. 

Inulin is a substance found in the roots of dahlias and 
other plants. It is soluble in hot water, insoluble in alcohol 



AESCULIN. 375 

It is laevo-rotatory, [a]^= — 36.57 , and is converted into 
1-fructose by boiling with dilute acids. 

Arabin, C 10 H 18 O 9 (?), is the chief constituent of gum arable. 
It resembles dextrin in its general properties, but is con- 
verted to arabinose, C 5 H 10 O 5 , by boiling with dilute acids. 

Xylan is a gumlike material found in straw, and probably 
in corncobs, wheat, bean, and many other vegetable mate- 
rials. It is converted to xylose, C 5 H 10 O 5 by boiling with 
dilute acids. As xylan, and perhaps other bodies called 
pentosans, form a considerable portion of straw, hay, and 
other food materials used for cattle and horses, the question 
of their food value is one of some importance, but one 
which has not yet been satisfactorily answered. The deter- 
mination of these constituents is effected by boiling the 
materials with dilute acids which first hydrolyze them to 
xylose, which is then further converted into furfural (p. 360). 

Glucosides. — There are found in nature a considerable 
number of vegetable substances which yield, by hydrolysis, 
a sugar and some other characteristic compound or com- 
pounds. Such bodies are called glucosides. The hydrolysis 
may usually be effected by means of dilute acids, but is also 
often caused by some special enzyme, or ferment, which 
accompanies the glucoside. The sugar formed is usually 
glucose, but rhamnose, mannite, phloroglucinol, and other 
compounds are occasionally produced. More than a hun- 
dred glucosides have been studied with some care, and, 
doubtless, very, many more exist. Only a few of the most 
interesting can be mentioned. 

Aesculin, C 15 H 16 9 +iJH 2 0, is found in horse-chestnuts. 
It gives, with dilute acids, or with the enzyme, emulsin, 
glucose and aescicletin, 



376 ORGANIC CHEMISTRY. 

(HO) 2 C c H 2 ^ = ^-CO + H 2 0. 

Amygdalin, C 2 oH 27 NO n -J- 3H 2 0, is found in bitter almonds, 
in peach stones, and in the seeds of apples and pears, etc., 
it is hydrolyzed by dilute acids, or emulsin, to glucose, benz- 
aldehyde, and hydrocyanic acid (p. 182). 

Coniferin, C 16 H 22 8 + 2H 2 0, is found in the cambium of 
the conifers and in asparagus. It gives, with dilute acids, 
glucose and a resin ; with emulsin it is slowly hydrolyzed to 
glucose and coniferyl alcohol, CH 3 O.C 6 H 3 (OH) . C 3 H 4 OH. 
By oxidation with chromic acid it gives vanillin (p. 186). 

Digitalein, C 22 H 38 9 , is found in the leaves of Digitalis 
purpurea. It is decomposed by dilute acids into glucose 
and digitalireti?i, C 16 H 26 3 . 

Tannins are acid glucosides, found in oak-bark, sumac, 
tea-leaves, canaigre root, and many other plants. Most of 
them yield a sugar, which is not always glucose, and other 
substances, on boiling with dilute acids. Their great com- 
mercial value depends on the fact that they unite with sub- 
stances found in the skins of animals forming non-putre- 
factive compounds. They all give green or blue color re- 
actions with ferric chloride. The value of tanning materials 
is determined by preparing an aqueous extract, and treating 
this with some hide powder, which combines with the tannin. 
The difference between the total solid matter contained in 
the original extract and that contained in the extract after 
treatment with the hide powder furnishes the data necessary 
for the determination. 

Indican, C 26 H 31 N0 17 , is found in the wood /satis tinctoria 
of the East Indies. In the manufacture of indigo it is 



PHLORIZIN. 377 

hydrolyzed by a ferment which forms when the plant is 
covered with water and exposed to the air. It is also hydro- 
lyzed by boiling with dilute acids, giving indiglucin and 
indigo blue. 

2C 26 H 31 N0 17 + 4 H 2 = 6QH 1 o0 6 +C 16 H 10 N 2 2 . 

Indiglucin. Indigo blue. 

The value of the indigo prepared in this manner from vege- 
table sources during the year 1900 was about $15,000,000. 

Iridin, C 24 H 26 13 , is found in violet root. It gives, when 
heated with dilute sulphuric acid and alcohol, glucose and 
irigenin, C 18 H 16 8 . The body which gives to violet root its 
pleasant odor is not iridin but irone (p. 197). 

Myronic Acid, C 10 H 17 NS 2 O 9 , is found in the seed of the 
black mustard in the form of its potassium salt, 

C 10 H 16 NS 2 O 9 K + H 2 0, 

called sinigrin. Under the fermentative action of myrosin, 
an enzyme found in white mustard, sinigrin yields glucose, 
acid potassium sulphate, and allyl isothiocyanate or allyl 
mustard oil. 

C 10 H 16 NS 2 O 9 K + H 2 O = C 6 H 12 6 + C 3 H 5 NCS + KHS0 4 . 

Phlorizin, C 21 H 24 O 10 + 2H 2 0, is found in the bark of the 
roots of apple, cherry, and plum trees. It is hydrolyzed by 
acids to glucose and phloretin, C 15 H 14 5 . Phloretin, in turn, 
yields, on boiling with a solution of potassium hydroxide, 
fihloroglucinol) 

/OH 1 
C 6 H 3 -OH 3, 
\OH 5 
and fihloretic acid, 

CH<^ H * 

t6tl4 \OH 4 



378 ORGANIC CHEMISTRY. 

Salicin, C 13 H 18 7 , is found in willow bark and leaves, and 
in several other plants. It is hydrolyzed by emulsin, or by 
ptyaline, an enzyme formed in the saliva, to glucose and 
saligenin or o-hydroxy benzyl alcohol, 

CH 2 OH i 
QHl< OH 

Salicin is intensely bitter. It is used in medicine. It is 
oxidized by nitric acid to kelicin, 

C 6 H 4 -CHO 
> 

QH i; o 5 

Saponin, C 32 H 52 17 , is found in soap root {saponaria offi- 
cinalis). It gives, with dilute acids, sugar and sapogenin, 
C 14 H 22 2 . Saponin gives, with water, a suds very much like 
that produced by soap. The soap-root is used in some 
places instead of soap. 

Solanine, C 52 H 93 N0 18 , is a basic glucoside, found in deadly 
nightshade {solarium nigrum) and in potato-balls. It gives, 
with acids, solanidine, C 40 H 61 NO 2 , and sugar. Solanine is a 
poison. 

Bitter Principles. 

Mention may be made here of the so-called " bitter prin- 
ciples," natural compounds, mostly of vegetable origin, 
which contain only carbon, hydrogen, and oxygen. To this 
class belong absinthin, aloi'n, anemonin, cantharidin, cap- 
saicin, cascarin, picrotoxin, and more than one hundred 
other substances. Some of these have medicinal value, 
others are poisons. In a few cases they have been studied 
in careful detail, and the structure has been established, but 
about the majority of them very little is known. 



LABORATORY EXERCISES. 379 

Laboratory Exercises. 

1. Determination of the specific rotation of various sugars. 

2. Determination of cane sugar and invert sugar in molasses. 

3. Determination of starch in some grain, as corn or wheat. 

4. Preparation of glucosazone. 

5. Test of urine for glucose. 



380 ORGANIC CHI: MIS TRY. 



CHAPTER XVIII. 

HALOGEN COMPOUNDS. 

Very few, if any, halogen organic compounds arc found 
in nature. Such compounds arc, however, of very con- 
siderable importance, and it has been necessary to refer to 
many of them in the preceding pages. Some methods of pre- 
paring them, and some of their properties, have also been 
incidentally mentioned. 

Those substances which contain chlorine, bromine, and 
iodine are of most importance, compounds of fluorine* 
being comparatively rare and unimportant. 

Methods of Preparation. 

i. Direct substitution of a halogen atom for hydrogen, 
As chlorine and bromine are very active agents, it is possi- 
ble to obtain many halogen compounds by the direct action 
of these elements upon hydrocarbons and their derivatives. 
Thus chlorine may give the following series of reactions with 
methane : 

CH 4 +Cl a =CH 8 Cl + HCl. 

Methyl chloride, 

cii 3 ci+ci,=cu,a,+nci. 

Methylene 
chloride. 

* V. Meyer and Jacohson do not, apparently, include fluorine among the halogens. 
There seems to be no logical reason for excluding it, ''however, and it will be so included 
here. 



HALOGEN COMPOUNDS. 38 1 

CH 2 C1 2 + C1 2 =CHC1 8 +HC1. 

Chloroform. 

CHCl 8 -f-Cl 2 =CCl 4 +HCl. 

( '.11 bon 
tetrachloride. 

The products are also named, logically, monocklormetkane^ 
dichlormethane^ trichlormethane, tetrachlormethane. 

While this series of reactions is of great theoretical inter- 
est, and similar reactions are of considerable importance for 
the identification of hydrocarbons of the marsh-gas series, it 
is practically impossible, in that series, to limit the reaction 
to the formation of a single compound; and the isolation of 
the different substances formed is attended with considerable 
difficulty. 

The halogen derivatives of the hydrocarbons are distin- 
guished as primary ', secondary, and tertiary in the same sense 
as the alcohols (p. 136) ; thus : 

CH 8 CH 2 CH 2 CH 2 C1 

is primary butyl chloride. 

CH 8 CH 2 CHC1CH 8 

is secondary butyl chloride. 

CM 
CH, 



>CC1-('IL 



■.', 
is tertiary isobutyl chloride. 

The official names, i-chlorbutane, 2-chlorbutane, and 
2 -chlor-2 -methyl propane, are also used, and are to be pre- 
ferred. 

When chlorine acts upon the normal homologues of meth- 
ane, both primary and secondary chlorides are formed. 
Pentane gives 

CH 8 CH 2 CH a CH 2 CH 2 Cl and CH 8 CH 2 CH a CHClCH 8 . 



382 ORGANIC CHEMISTRY. 

Hydrocarbons containing a tertiary hydrogen atom give the 
tertiary chloride. Isobutane gives 

^>CC1CH 3 . 

A second atom of chlorine combines with the same carbon 
atom as the first. Ethyl chloride gives ethylidene chloride, 
CH 8 CHC1 2 , not ethylene chloride, CH 2 C1CH 2 C1. 

Bromine does not act upon hydrocarbons of the marsh- 
gas series at ordinary temperatures. By heating in sealed 
tubes substitution products can be obtained. 

Halogen substitution products can be obtained from un- 
saturated hydrocarbons and their derivatives by the direct 
action of the elements only when the addition, which occurs 
at first, is followed by a loss of hydrochloric or hydrobromic 
acid. In the aromatic series, even, where the action usually 
has every appearance of being a direct substitution, it is 
probable that addition takes place at first : 

H H HBr 

C C C 

// \ # \ / \ 

HC CH HC CHBr HC CH 

I II -> I I or || || 

HC CH HC CHBr HC CH 

^ / % / \ / 

c c c 

H H HBr 

H Br 

C C 

// \ // \ 

HC CBr HC CH 

-> I || or I || 

HC CH HC CH 

^ / % / 

C C 

H I 

H 



LAWS OF POSITIONS OF SUBSTITUTING GROUPS. 383 

Chlorine and bromine enter the nucleus when they act 
upon homologues of benzene in the cold, but they enter. the 
side chain when they act upon the boiling hydrocarbon. 
Thus toluene and rj-xylene give with bromine in the cold 
(best with the addition of a little iron to form ferric bromide, 
which greatly aids the action), fi-bromtoluene, 

QH 4<Br +) 

o-bromtoluene, CH 3 1 

QH 4 < Br 2 , 

and brom-p-xylene, / CH 3 1 

C 6 H 3 -Br 2. 

\CH 3 4 

The boiling hydrocarbons give, on the other hand, benzyl 
bromide, C 6 H 5 CH 2 Br, and p-xylylene bromide, 

CH 2 Br 1 
CeH4< CH 2 Br 4' 

The latter action takes place best in direct sunlight. 

Laws of Positions Taken by Substituting Groups. — Of still 
greater interest are the laws which govern the position which 
the halogen atom takes in the benzene nucleus with regard 
to other substituting groups. It is found that in the forma- 
tion of substitution products of benzene and its derivatives, 
whether the substituting group is chlorine, bromine, the nitro 
group (N0 2 ), or the sulphonic acid group (S0 2 OH), the 
ortho and para positions are intimately associated while the 
meta position stands by itself. Thus by the direct bromina- 
tion of toluene, C 6 H 5 CH 3 , a mixture of the ortho and para 
bromtoluenes, 

CH <r CH3 I 
^ 4< Br 2 and 4' 



384 ORGANIC CHEMISTRY. 

is formed, while benzoic acid, 

C 6 H 5 C0 2 H, 
gives, almost exclusively, metabrombenzoic acid, 

C0 2 H 1 
CeH4< Br 3' 

A careful study of the matter has shown that the substi- 
tuting atom or group enters chiefly in the para or ortho 
position with reference to CH 3 , C 2 H 5 , OH, -NH 2 , CI, Br, or 
I, but mainly in the meta position toward C0 2 H, S0 3 H, 
CC1 3 , N0 2 , CHO, or CN. Halogen substitution products 
cannot, however, be obtained directly from compounds con- 
taining the last two groups. 

In general, it may be stated that positive groups cause a 
substituent to enter in the ortho or para position, while nega- 
tive groups throw it to the meta position ; but, curiously 
enough, hydroxyl, chlorine, bromine, and iodine are associ- 
ated, in their effect, with the positive groups. 

No explanation for these laws of substitution has been 
generally accepted. They are, perhaps, due to the forma- 
tion of addition products ; thus toluene may give, at first, 
the compounds : 



CH a 




Br 




CH 3 




Br 


\ 


C 


/ 




\ 


C 


/ 


/ 
CH 

II 
CH 




CHBr 

1 
CH 


and 


/ 
CH 

II 
CH 




\ 
CH 

CH 


\ 


c 

1 

11 


// 




\ 

/ 
H 


C 


/ 

\ 
Br 



HALOGEN SUBSTITUTION PRODUCTS OF ACIDS. 385 

The former would give, by loss of hydrobromic acid, 
orthobromtoluene, while the latter would give parabromtolu- 
ene. It may be that benzoic acid gives the addition com- 
pounds : 



C0 2 H 

1 




C0 2 H 
1 


1 

c 




1 
C 


CH CH 

II 1 
CH CHBr 


and 


CHBr CH 

1 1 
" CH CHBr 


\ / 
CH 




CH 



I 

Br 
Either of these may give the metabrombenzoic acid by 
loss of hydrobromic acid. 

Halogen Substitution Products of Acids. — In preparing 
halogen substitution products of the aliphatic acids it has 
been found that the chlorides 



R— C ), or bromides 



(*-<*) 



of the acids react much more easily than the free acids. In 
practical work the acid is either first treated with phosphorus 
pentachloride and the mixture of acid chloride and phos- 
phorus oxy chloride then acted upon with bromine ; or the 
acid is mixed with red phosphorus and the bromine added 
slowly : 

CH 3 CH 2 C0 2 H + PC1 5 = CH 3 CH 2 COCl + POCl 3 + HC1 

CH 3 CH 2 COCl + Br 2 = CH 3 CHBrCOCl + HBr. 

Or 3CH 8 CH 2 C0 3 H + P + iiBr = 3CH 3 CHBrCOBr 

+ HP0 3 + 5HBr. 



386 ORGANIC CHEMISTRY. 

The chloride or bromide of the acid can be decomposed 
by treatment with water or with glacial formic acid : 

CH 8 CHBrCOCl + HC0 2 H = CH 3 CHBrC0 2 H + CO + HC1. 

a-Brompropionic acid. 

V 

It has been found that only those aliphatic or alicyclic 
acids which contain hydrogen in the a-position with reference 
to the carboxyl (i.e. those containing the group, 

R-CH 2 -C0 2 H, 
° r ^>CHC0 2 H), 

can be brominated in this manner, and that the bromine 
always enters in the a-position. Since the bromine of the 
broni acids obtained may be replaced by hydroxyl, or may 
be eliminated with a neighboring hydrogen atom, giving an 
a-/3-unsaturated acid, the preparation of such a-brom-acids 
has often proved of great practical importance. 

Many other organic compounds may give halogen deriva- 
tives by direct substitution, but a further discussion of this 
method of preparation seems to be unnecessary. 

2. By direct addition to unsaturated or cyclic compounds. 
In general chlorine and bromine add themselves to unsat- 
urated compounds in such amount as to give a halogen 
derivative of the corresponding saturated aliphatic or ali- 
cyclic compound. Iodine also adds itself to such com- 
pounds, but less easily, and the resulting iodine derivatives 
are unstable. 

Derivatives of cyclopropane also take up bromine directly. 

PTT 

Thus cyclopropane, CH 2 < i 2 , gives trimethylene bromide 

CH 2 

(i, 3-dibrompropane), CH 2 BrCH 2 CH 2 Br. 



HALOGEN SUBSTITUTION PRODUCTS OF ACIDS. 387 

Benzene adds six chlorine or six bromine atoms directly, 
in the sunlight ; but the resulting compounds are decomposed 
by heat, giving 1,2,4 trichlor- or tribrombenzene and hydro- 
chloric or hydrobromic acid. 

3. By the addition of- hydrochloric, hydrobromic, or 
hydriodic acid to unsaturated compounds. In accordance 
with the " positive negative" law (p. 191) the halogen 
atom adds itself to the carbon atom bearing least hydrogen, 
or to the carbon atom farthest removed from a carboxyl 
group : 

CH 3 CH = CH 2 gives CH 3 CHICH 3 , 

Propylene. Isopropyl iodide. 

CH 2 = CHC0 2 H gives CH 2 BrCH 2 CG 2 H. . 

/3-brompropionic acid. 

When y-brom-acids are formed in this manner they are 
usually unstable, and pass very readily into lactones (p. 318). 

4. By the replacement of hydroxyl by chlorine, bromine, 
or iodine. Alcohols and hydroxyl derivatives are very com- 
mon among natural organic substances ; and, since they are 
much more reactive than the hydrocarbons, they are espe- 
cially suitable for the preparation of halogen compounds. 
In some cases the alcohols will react directly with the halo- 
gen acids, as, 

CH.OH + HI = CH 3 I + H 2 0. 

Methyl iodide. 

More usually a chloride, bromide, or iodide of phosphorus 
is allowed to act upon the alcohol or hydroxyl compound. 
The compound of phosphorus may be prepared before addi- 
tion to the alcohol, or, in the case of stable compounds, the 
alcohol may be mixed with red phosphorus and the bromine 
or iodine added slowly : 



388 ORGANIC CHEMISTRY. 

3 CH 3 CH 2 OH + P-r3Br = 3CH 3 CH 2 Br + H 3 P03, 
5 CH 3 OH + P + 5l = 5CH 3 I + H 3 P0 4 +H 2 0, 

C 6 H 5 OH + PCl 5 =C 6 H 5 Cl+POCl 3 +HCl. 

Phenol. Monochlor- 

benzene. 

The hydroxyl group in phenols is replaced with much 
greater difficulty than that in aliphatic compounds. 

5. By the action of phosphorus pentachloride or penta- 
bromide upon aldehydes or ketones. This gives compounds 
in which two chlorine or bromine atoms are combined with 
the same carbon atom. 

^o 

CH 3 C - H + PC1 S = CH,CHC1 2 + POC1, 

Aldehyde. Ethylidene chloride. 

CH 3 COCH 3 + PBr 5 = CH 3 CBr 2 CH 3 + POBr 3 . 

Acetone. 

6. By the action of cuprous chloride or bromide or 
hydriodic acid upon a halogen salt of a diazo-compound. 
(See p. 460). This reaction is extremely useful for the re- 
placement of an amino group by a halogen atom in the 
aromatic series. 

7. By the action of alcoholic potash or soda upon a 
dihalogen compound. Attention has already been called to 
the fact that substitution products cannot be obtained from 
unsaturated compounds directly. The method here given 
makes it possible to obtain such substitution products indi- 
rectly. Thus ethylene gives, with bromine, ethylene bromide, 
CH 2 BrCH 2 Br ; and this, on treatment with alcoholic potash, 
loses hydrobromic acid with formation of vinyl bromide 
(monobromethylene) : 

CH 2 BrCH 2 Br + KOH = CHBr=CH 2 + KBr-f-H 2 0. 

Vinyl bromide. 



GENERAL PROPERTIES OF HALOGEN COMPOUNDS. 389 

8. By the action of hypochlorites, hypobromites or hypo- 
iodites upon compounds containing the group COCH, 3 , or 
upon 1,3-diketones. The reaction gives rise only to the 
formation of chloroform, CHBr 3 , bromoform, CHBr 3 , or 
iodoform, CHI 3 . It appears to consist at first in the substi- 
tution of halogen for hydrogen in the CH 8 group, followed by 
a hydrolysis which is closely related to the " acid decom- 
position " of acetoacetic ester. 

2CH 3 COCH 3 + 3 CaO 2 Cl 2 -:2CH3COCCl 3 -f3Ca(0H) 2 

Acetone. Trichloracetone. 

2CH 3 COCCl 3 + Ca(OH) 2 = Ca(CH 3 C0 2 ) 2 + 2 CHCl 3 . 

Chloroform. 

The action of sodium hypochlorite upon dihydroresorcinol 
has been given (p. 159). This last reaction has not been 
studied for a sufficient number of cases to make sure that it 
is general in its application, but it seems likely that it will 
prove so. 

General Properties of Halogen Compounds. — In general, the 
organic halogen compounds are liquids or solids with boiling 
points which increase with their molecular weights, or with a 
decrease of the amount of hydrogen which they contain. 
Only methyl chloride, CH 3 C1, methyl bromide, CH 3 Br, ethyl 
chloride, C 2 H 5 C1 and a few fluorine compounds of low molec- 
ular weight, are gases at ordinary temperatures. 

In general, the halogen compounds resemble, in solubility, 
the bodies from which they are derived. Halogen substitu- 
tion products of the hydrocarbons are nearly insoluble in 
water, but are usually soluble in alcohol, ether, and ligroin. 

In chemical conduct, the halogen compounds of carbon dif- 
fer very markedly from the halogen compounds of other ele- 
ments. The metallic halides, with very few exceptions, ionize 



390 ORGANIC CHEMISTRY. 

readily in water, and give immediate precipitates with silver 
nitrate in aqueous and alcoholic solutions, while halogen 
compounds of the non-metals react more or less violently 
with water to form halogen acids and acids of the non-metallic 
elements. Organic halogen compounds, on the contrary, do 
not ionize to such a degree as to exhibit electrical conductiv- 
ity in aqueous or alcoholic solutions, and they will react with 
silver nitrate in only a few cases. On account of these facts 
the metallic halogen compounds are spoken of as electro- 
lytes, while the organic halogen compounds are usually con- 
sidered to be non-electrolytes. 

A careful study of the matter would seem to indicate, 
however, that the difference is one of degree rather than 
of kind. The organic halogen compounds show as great, 
or even a greater difference, among themselves, than 
that between organic and inorganic compounds. Acetyl 
chloride, 

CH„C' 



3~\ 



CI 



reacts violently with water, and the chlorides of the acids, 
generally, react in a manner which resembles closely the con- 
duct of the halogen compounds of the non-metallic elements. 
Methyl iodide, CH 3 I, in an alcoholic solution, gives an im- 
mediate precipitate with silver nitrate ; but chloroform, 
CHClg, reacts with silver nitrate very slowly indeed, while 
monochlorbenzene, C 6 H 5 C1, may be boiled with a solution of 
silver nitrate without the formation of an amount of silver 
chloride which can be detected. These facts find their most 
simple explanation by the assumption that organic halogen com- 
pounds ionize, but that the degree of ionization is so slight 
as to be of a different order of magnitude from the ionization 
of most inorganic compounds. 



AROMATIC AND ALIPHATIC HALOGEN COMPOUNDS. 39 1 

Differences Between Aromatic and Aliphatic Halogen Com- 
pounds. — The difference between methyl iodide and chlor- 
benzene, referred to above, is a characteristic difference 
between aliphatic and aromatic compounds. Aliphatic halo- 
gen compounds react more or less easily with water, or with 
silver oxide and water, giving alcohols ; with potassium acetate 
or silver acetate, giving acetyl derivatives of alcohols ; with 
potassium cyanide, giving cyanides, or nitriles ; with silver 
cyanide giving isocyanides; with silver nitrite, giving nitro 
compounds ; with sodium alcoholates, giving ethers ; with so- 
dium malonic ester and sodium acetoacetic ester, giving deriv- 
atives of these compounds ; and with ammonia giving amines. 

In general, the iodides react most easily, the chlorides with 
considerably greater difficulty, while the bromides occupy an 
intermediate position. The reactivity also decreases with 
increasing molecular weight, and is greater for primary than 
for secondary, and for secondary than for tertiary halogen 
compounds. These general statements are subject, however, 
to some exceptions and modifications, and the order of reac- 
tivity for one reaction is not necessarily that for another. 
Methyl iodide occupies a somewhat unique position, giving, 
in some reactions, a rate which is ten-fold that of ethyl 
iodide. 

Aromatic compounds having the halogen in the side chain 
are to be considered as virtually aliphatic compounds, so far 
as the reactivity of the halogen atoms is concerned. Thus, 
benzyl chloride, C 6 H 5 CH 2 C1, reacts readily with potassium 
cyanide, ammonia, and the other reagents mentioned above. 
When the halogen is combined with the nucleus, however, it 
reacts, as a rule, only with very vigorous agents or at a high 
temperature, as, for instance, with melted caustic potash. In 
a few cases only, the presence of nitro groups renders a halo- 
gen atom more reactive. Thus chlortrinitrobenzene, 



392 ORGANIC CHEMISTRY. 



CI i 
QH 2 < 

N0 2 6 



N0 2 2 
^N0 2 4 



is changed to picric acid, C 6 H 2 (N0 2 ) 3 OH, by boiling with a 
solution of sodium carbonate, and to trinitraniline, 

C 6 H 2 (N0 2 ) 3 NH 2 , 

by treatment with ammonia. 

Reduction of Halogen Compounds. — By reducing agents, 
halogen atoms can be replaced by hydrogen, and so the hy- 
drocarbon or mother substance of the halogen derivative re- 
generated. A great variety of reagents may be employed for 
the purpose, the most important being sodium amalgam, with 
water, alcohol, or glacial acetic acid ; sodium and moist ether, 
sodium and absolute alcohol, or amyl alcohol ; zinc with water 
and alcohol, with sulphuric or hydrochloric acid, or with am- 
monia or sodium hydroxide ; and hyriodic acid. With com- 
pounds having two halogen atoms combined with adjacent 
carbon atoms, the first effect of the reduction seems to be 
merely to remove the halogen. Thus ethylene bromide, 
CH 2 BrCH 2 Br, gives ethylene, CH 2 = CH 2 , by reduction with 
zinc and alcohol. 

Halogen Derivatives of Acids. 

The halogen derivatives of the acids differ in their conduct 
according to the position of the halogen atom or atoms, and 
the differences are of considerable practical importance for 
synthetical purposes and in the study of the structure of 
unsaturated acids. 

a-Halogen Acids. — If the halogen is in the a-position, the 
compounds are generally more stable than acids with the 



HALOGEN ACIDS. 393 

halogen in the (3- or y-position. By treating a-halogen acids 
with silver oxide and water, or by boiling them with sodium 
carbonate or barium hydroxide, or with water alone, a-hydroxy 
acids can usually be obtained. Thus a-chlorisovaleric acid 
(2 chlor-3-methylbutanoic acid), 

^ 3 >CH-CHClCOoH, 

gives, with barium hydroxide, a-hydroxyisovaleric acid, 

™ 3 >CHCH(OH)C0 2 H. 

The action of alcoholic potash, or of sodium ethylate, on 
the other hand, usually gives an unsaturated acid. Thus 
a-bromisovaleric ester, 

™ 3 > CHCHBrC(XC 2 H 6 , 

gives, with sodium ethylate, C 2 H 5 ONa, in alcoholic solution, 
a mixture of dimethylacrylic, 

CH g 

CH 3 
and a-ethoxy isovaleric, 



>C = CHC0 2 CH 5 , 



CH3 >CH — CH<° C2Hs 
CH 3 C0 2 C 2 H 5 

esters. 

/3-Halogen Acids are less stable, decomposing more easily 
on standing or when heated. When warmed with a solution 
of sodium carbonate there may be formed : an unsaturated 
hydrocarbon, the halogen acid and carbon dioxide ; an un- 
saturated acid ; or a hydroxy-acid. It is sometimes possible 
to give predominance to one or the other of these decomposi- 
tions by changing the conditions. The use of only a little 



394 ORGANIC CHEMISTRY. 

more than the calculated amount of sodium carbonate favors 
the first reaction ; the use of an excess of sodium carbonate, 
or of sodium or barium hydroxide, favors the third reaction 
(hydroxy acid) ; while alcoholic potash, or soda, will give 
chiefly the unsaturated acid. To illustrate, ^-brom-2-methyl- 
butanoic acid, 

CH 3 -CHBr-CH-C0 2 H, 

I 
CH 3 

may decompose to give the following products : 

i. CH 3 CH = CH-CH 3 , HBr and C0 2 . 

2. CH 3 -CH = C-C0 2 H. 

I 
CH 3 

3. CH 3 CH(OH)-CH-C0 2 H (?) 

I 
CH 3 

y-Halogen Acids are, usually, very unstable, and pass spon- 
taneously, or, at most, by boiling with water, into lactones. 
Thus y-bromvaleric acid, 

CH 3 CHBrCH 2 CH 2 C0 2 H, 

gives valero lactone, 

CH 3 — CH — CH 2 CH 2 

I I • 

O CO 

Unsaturated' acids may sometimes be obtained from such 
acids by treating their esters with alcoholic potash or so- 
dium ethylate. Thus y-bromisocaproic ester, 

nrr 

CH 3 > CBrCH 2 CH 2 C0 2 C 2 H 5 , 



gives, with sodium ethylate, pyroterebic ester, 



METHYLENE IODIDE. 395 

CTT 

SC = CH- CH 2 C0 2 C 2 H 5 . 

Dihalogen derivatives of the acids conduct themselves as 
is to be expected frpm the conduct of monohalogen deriva- 
tives. Thus : 

Na 2 C0 3 . 

CH 3 CHBrCHBrC0 2 H ->- CH 8 CH = CHBr, HBr and C0 2 ; 

Crotonic dibromide. a-Brompropylene. 

Alcoholic 
potash. 

->- CH 3 CH = CBrC0 2 H + HBr; 
CH 2 BrCHBrCH 2 CH 2 C0 2 H -i ' CH 2 BrCH-CH 2 CH 2 

7-S-Dibrom-7^-valeric acid. 
(4,5-Dibrompentanoic acid). ' ' 

5-Brom 1,4-pentanolid. 

Methyl Iodide, CH 3 I, is prepared by mixing methyl alcohol 
with some red phosphorus, adding, in portions, with cooling, 
eighty to ninety per cent of the calculated amount of iodine, 
and distilling after some time. Methyl iodide boils at 42. 5 °, 
and has a specific gravity of 2.2852 at 15 . It is very reac- 
tive, and is extensively used for the introduction of methyl 
groups in a great variety of organic syntheses. 

Methylene Iodide, (diiodomethane) CH 2 I 2 , is prepared by 
heating iodoform with hydriodic acid and phosphorus : 

CHI 3 +HI = CH 2 I 2 +I 2 . 

Iodoform. Methylene 

iodide. 

P+5l+4H 2 = H 3 P0 4 + 5 HI 

Methylene iodide solidifies at o°, and melts at 4 . It 
boils, with partial decomposition, at 180 . Its specific 
gravity is 3.2853 at 15 °. It is sometimes used to separate 
minerals of different specific gravities. Moissan used it to 
separate diamonds from graphite. 



396 ORGANIC CHEMISTRY. 

Iodoform (triiodomethane), CHI 3 , is formed when alcohol, or 
a substance containing the group — COCH 3 , is treated with 
a solution of sodium carbonate and iodine (p. 199). The 
iodoform reaction is often used for the detection of alcohol, 
but it must be remembered that a considerable number of 
other substances give the reaction. Iodoform crystallizes in 
hexagonal plates, which melt at 119 . It is volatile with 
water vapor, and has a peculiar odor, which is unpleasant to 
most people. It is a powerful germicide, and is much used 
in dressing wounds. 

Bromoform (tribrommethane), CHBr 3 , is prepared in the 
same manner as chloroform. It melts at 7. 6°, and boils at 
15 1.2 . Its specific gravity is 2.9045 at 15 . 

Chloroform (trichlormethane) was formerly prepared by the 
action of " chloride of lime " upon alcohol. The first action 
is partly oxidation and partly chlorination, giving trichloral- 
dehyde, which is then decomposed by the calcium hydroxide : 

2 CH 3 CH 2 OH + 4 CaClX> 2 

= 2CCl 3 CHO + CaCl 2 + 3 Ca(OH) 2 + 2H 2 0. 

Trichloraldehyde. 

2 CCl 3 CHO + Ca(OH) 2 = 2 CHC1 3 + Ca(CH0 2 ) 2 . 

Calcium formate. 

The reaction is not altogether a clean one, and the chloro- 
form prepared by it is somewhat difficult to purify. There- 
fore, for anaesthetic purposes, chloroform was formerly often 
prepared by the decomposition of trichloraldehyde (chloral) 
with caustic potash : 

CCl 3 CHO + KOH = CHC1 3 + KHC0 2 . 

At present chloroform is largely prepared by the use of 
acetone (pp. 188, 199, and 389). 

Chloroform is a colorless, heavy liquid, with a sweetish 
odor. It boils at 61.2 , and has a specific gravity of 



CHLOROFORM. 397 

o 00 

1.52637 at — , or 1.5039 at — L_ . it melts at — 70 . It is 

4 4 

very slightly soluble in water. Pure chloroform is not very 
stable. It decomposes slowly when exposed to air and light, 
giving free chlorine, hydrochloric acid, phosgene (COCl 2 ), 
and other products. The presence of a small amount (1%) 
of alcohol renders it more stable, and commercial chloroform 
often contains alcohol for that purpose. The decomposition 
products are much more poisonous than chloroform, and it 
is very important that the chloroform used for anaesthesia 
should be pure. Pure chloroform gives, at most, only a very 
faint opalescence when shaken with a solution of silver 
nitrate. 

Chloroform seems to inhibit the growth of most micro- 
organisms without killing them, unless its action is too 
prolonged. Its use as an anaesthetic is familiar to every 
one. The proportion of fatalities in the use of the more 
common anaesthetics is as follows : 

Pental (3 in 631) 1 in 211 cases. 

Chloroform j. in 2075 

Bilroth's mixture 1 in 3370 

Ether 1 in 5 112 

Ethyl bromide 1 in 5396 

Chloroform-ether 1 in 7613 

These statistics are based on a total of 330,429 cases, the 
total number of deaths being 136, or one in 2429 cases. 

Carbon Tetrachloride (tetrachlormethane), CC1 4 , may be 
obtained by the action of chlorine upon chloroform. It is 
most easily prepared by passing dry chlorine into a boiling 
mixture of carbon bisulphide and antimony trichloride. Car- 
bon tetrachloride is a liquid which boils at 76.74 , and has 

a specific gravity of 1.6084 at ^^- • It solidifies at — 19.5 

4 



398 ORGANIC CHEMISTRY. 

under a pressure of 210 atmospheres, at o° with a pressure 
of 620 atmospheres, and at 19. 5 with a pressure of 1160 
atmospheres. 

When sulphuric anhydride acts upon carbon tetrachloride, 
phosgene and pyrosulphuryl chloride are formed : 

CC1 4 + 2 S0 3 = COCl 2 + S 2 5 C1 2 . 

Ethyl Chloride, CH 3 CH 2 C1, is formed very slowly when 
hydrochloric acid acts upon alcohol. It is prepared by pass- 
ing hydrochloric acid into alcohol containing anhydrous zinc 
chloride. It is a gas at ordinary temperatures, but can be 
easily condensed to a liquid by a freezing mixture, and can 
be preserved in sealed tubes. It is manufactured on a large 
scale as a step in the manufacture of " sulfonal " (p. 486). 

Ethylene Chloride, CH 2 C1 ■ CH 2 C1, and ethylidene chloride, 
CH 3 CHC1 2 , have been considered in the discussion of the 
structure of ethylene (p. 78). 

The following tabular statement of the chlorine deriva- 
tives of ethane is of some interest as showing the connection 
between composition, structure, and physical properties : 

Name. Formula. 

Chlorethane .... CH 3 CH 2 C1 

( i.i.Dichlorethane . . CH S 'CHC1 2 

I i. 2 .Dichlorethahe . . CH 2 C1'CH 2 C1 

( i.i.i.Trichlorethane . . CH 3 CC1 3 

I i.i.2.Trichlorethane . CH.ClCHCh 

( i.i.i.2.Tetrachlorethane, CH 2 C1CC1 3 

< i.i.2.2.Tetrachlorethane, CHC1 2 CHC1 2 

Pentachlorethane . . CHC1 2 CC1 3 

Hexachlorethane . . CC1 3 CC1 3 

It will be seen that, of two isomers, the symmetrical com- 
pound always has a higher boiling point and a higher 
specific gravity. 



Boiling 


Sp. Gr. 


Point. 


AT O . 


12.5 


0.9214 


57-5° 


1.2 124 


83-5° 


I.2808 


74-5° 


I-3657 


114.0 


I.4784 


130.0 


I.5825 


i47-o° 


I.6258 


161. 7 


I.7089 


185.0 


2.0II 



PERBROMETHYLENE. 399 

Ethyl Bromide, C 2 H 5 Br, can be prepared by dropping bro- 
mine into a mixture o£ red phosphorus and ethyl alcohol. 
It is best prepared by mixing equal weights of ethyl alcohol 
and concentrated sulphuric acid, adding the mixture, which 
contains ethyl sulphuric acid, to a mixture of water and 
potassium bromide, and distilling : 

C 2 H 5 HS0 4 4- KBr = C 2 H 5 Br + KHS0 4 . 

Ethyl bromide is a volatile oil with a pleasant odor. It 
boils at 38. 37 , and has a specific gravity of 1.4500 at 15 . 
It is sometimes used as an anaesthetic, especially for the 
extraction of teeth. For this purpose red phosphorus, 
which usually contains arsenic, should not be used in its 
preparation. 

Ethylene Bromide, CH 2 BrCH 2 Br, is prepared by passing 
ethylene into bromine till the color of the latter is discharged. 
It melts at 9. 53 , boils at 131. 6°, and has a specific gravity 
of 2.1785 at 20 . 

Bromethylene (vinyl bromide) is prepared by the action of 
alcoholic potash upon ethylene bromide : 

CH 2 BrCH 2 Br + KOH = CH 2 = CHBr+KBr + H 2 0. 

Vinyl bromide boils at 1 6°, and has a specific gravity of 

i4° 
1. 5167 at— 5-- Vinyl bromide is absorbed by concentrated 
4 

sulphuric acid ; and the solution gives, on distillation, cro- 
tonic aldehyde, CH 3 CH = CH-CHO (p. 177). (What is 
the relation between this reaction and the conduct of ethy- 
lene toward concentrated sulphuric acid (p. 161)? 

Perbromethylene, CBr 2 = CBr 2 , is formed by the action of 
bromine upon alcohol or ether, or upon silver acetylide: 

CH = CAg4-6Br = CBr 2 =CBr 2 +AgBr-{-HBr. 



400 ORGANIC CHEMISTRY. 

Perbromethylene crystallizes in plates which melt at 53°. 
It is volatile with water vapor. 

Ethyl Iodide, C 2 H 5 I, is prepared from ethyl alcohol, red 
phosphorus, and iodine. It boils at 72.34 , and has a 
specific gravity of 1.9433 at 15 . 

Normal Propyl Iodide, CH 3 CH 2 CH 2 I, is prepared from 
normal propyl alcohol (from fusel oil), red phosphorus, and 
iodine. It boils at 102. 2 , and has a specific gravity of 

2 0° 

1.7427 at.— o ■ 
4 

Isopropyl Iodide (2-iodopropane), CH 3 CHICH 3 , is prepared 

by adding white phosphorus, in portions, to a mixture of 

glycerol, water, and iodine. The hydriodic acid formed 

from the interaction of iodine, phosphorus, and water acts 

upon the glycerol, partly as a reducing agent, and partly 

to replace the hydroxyl by iodine : 

CH 2 OHCHOHCH 2 OH+3 HI=CH 3 CHICH 3 + 3 H 2 0+I 2 . 

Isopropyl iodide boils at 89. 5 , and has a specific gravity 
of 1.7 109 at 1 5 . 

Allyl Bromide (i-brompropene), CH 2 =CHCH 2 Br, is pre- 
pared from allyl alcohol and phosphorus tribromide, or from 
allyl alcohol, potassium bromide, sulphuric acid, and water. 
It boils at 7o°-7i°, and has a specific gravity of 1.4336 at 

2-Brompropene, CH 2 = CBrCH 3 , is prepared by treating 
propylene bromide, CH 3 CHBrCH 2 Br, with alcoholic potash. 
It boils at 48°-49°, and has a specific gravity of 1.362 at 

2 0°. 

3-Brompropene, CHBr=CHCH 3 is also formed by treat- 
ing propylene bromide with alcoholic potash. It boils at 



BROMTOLUENE. 40 1 

60-6 1°, and has a specific gravity of 1.428 at 19-5°. What 
seems to be a stereomeric form is obtained by treating 1 . 1 , 
2-tribrompropane, CH 3 CHBrCHBr 2 , with zinc dust and alco- 
hol. It boils at 6 3 °-64°. 

Trimethylene Bromide (1,3-dibrompropane), 

CH 2 BrCH 2 CH 2 Br, 

is prepared by treating allyl bromide, CH 2 = CHCH 2 Br, with 
hydrobromic acid. It boils at 165 , and has a specific 

I7.° 

gravity of 1.9228 at — 5- • It gives cyclopropane, 
4 

CH 2 

I >CH 2 , 
CH 2 

when treated with zinc dust and alcohol of 75 per cent. 

Pinene Hydrochloride, C 10 H 17 C1, is formed by passing dry 
hydrochloric acid into turpentine. It melts at 125 , and 
boils at 210 . It closely resembles camphor in appearance 
and odor, and has been called artificial camphor. 

When pinene hydrochloride is treated with sodium acetate 
and glacial acetic acid at 200 , camphene, C 10 H 16 , is formed. 
A molecular rearrangement takes place in the reaction, but 
its nature is not fully understood. 

o-Bromtoluene, CH 3 1 

C « H4< Br 2' 

When toluene, to which a little iron has been added, is 
treated with bromine in the cold, a mixture of ortho- and 
parabromtoluenes is formed. If this mixture is cooled, the 
para compound separates in crystals, while the ortho com- 
pound remains liquid. The parabromtoluene can be puri- 
fied by crystallizing from alcohol. The portion remaining 
liquid after cooling in a freezing mixture consists chiefly 



402 ORGANIC CHEMISTRY. 

of the ortho compound. The pure orthobromtoluene is ob- 
tained from ortho-toluidine, 

LtH,< NH 2 2 ' 

by Sandmeyer's reaction (p. 460), or by distilling orthobrom- 
toluene sulphonic acid, 

/CH 3 1 
C 6 H 3 -Br 2, 

\S0 3 H 4 

with superheated steam. (Armstrong, J. Chem. Soc. (Lon- 
don), 45, 148; Kelbe, Ber. d. chem. Ges. 19, 93; Miller, J. 
Chem. Soc, 61, 1029). Orthobromtoluene melts at — 25. 9 , 

20° 

boils at 1 80. 6°, and has a specific gravity of 1.4222 at — ^ • 

4 

m-Bromtoluene, CH 3 1 

C 6 H 4<Br 3> 

is prepared from m-toluidine, 

C « H4< NH 2 3' 

by Sandmeyer's reaction (p. 460), or from metabrompara- 

toluidine, 

/CH 3 1 
C 6 H 3 -Br 3, 
\NH 2 4 

by the elimination of the amino group. It melts at —39. 8°, 

2 0° 

boils at 1 83. 7 , and has a specific gravity of 1.4099 at —3- • 

4 

p-Bromtoluene, CH 3 1 

CeH4< Br 4' 

is prepared by the direct bromination of toluene in the cold 



CHLORHYDRINS. 403 

(see above). It melts at 28. 5 , boils at 185.2 , and has a 

2 0° 

specific gravity of 1.3898 at — 5- • The three bromtoluenes 

4 
give the three xylenes, 

QH *<CH3' 

when treated with methyl iodide and sodium ; and these, in 
turn, give, by oxidation, the three phthalic acids, 

C0 2 H 
^ 6 4< C0 2 H* 

Benzylbromide, C 6 H 5 CH 2 Br, is formed by the action of 
bromine on boiling toluene, best in the direct sunlight. It 
boils at i98°-i99°, and has a specific gravity of 1.4380 at 

22° 

—3- • It gives, on oxidation, benzoic acid, C 6 H 5 C0 2 H. 
o 

Triphenylchlormethane, 

C 6 H 5 -CC1, 
QH 5 / 

is best prepared by the action of aluminum chloride upon 
a mixture of benzene and carbon tetrachloride. 

CC1 4 +3C 6 H 6 +A1C1 3 = (C 6 H 5 ) 8 CC1+ 3 HCH-A1C1 3 . 

Triphenylchlormethane melts at io8°-ii2°. It has ac- 
quired an especial interest from its use in the preparation of 
triphenylmethyl, (C 6 H 5 ) 3 C (p. 115). 

Chlorhydrins. 

The products formed by the replacement of a part of 
the hydroxyl groups of glycol, CH 2 OH ■ CH 2 OH, glycerol, 
CH 2 OH • CHOH • CH 2 OH, or other polyacid alcohols by 
halogen atoms, are called chlorhydrins, bromhydrins, etc. 



404 ORGANIC CHEMISTRY. 

They may be considered as halogen substitution products of 
alcohols, and are formed by the treatment of the polyacid 
alcohols with hydrochloric acid, or by the addition of hypo- 
chlorous acid to unsaturated compounds. 

Glycol Chlorhydrin (2-chlor-i-ethanol), CH 2 C1CH 2 0H, is 

prepared by treating glycol with hydrochloric acid, and is 
also formed by the addition of hypochlorous acid to ethy- 
lene : 

CHX)H CH C1 

I + HC1 = I + H 2 

CH 2 OH CH 2 OH 

CHo CH 2 C1 

|| " + HOC1 = I 

CH 2 CH 2 OH 

It is interesting to notice that in the latter reaction hypo- 
chlorous acid separates into CI and OH, and not into H and 
OC1, as would be expected of an acid. This fact is probably 
a clue to some other reactions of hypochlorous acid and of 
hypochlorites. 

Glycol chlorhydrin boils at i3o°-i3i°, and has a specific 
gravity of 1.2233 at o°. It is oxidized to chloracetic acid, 
CH 2 C1C0 2 H, by the chromic acid mixture. With caustic 
potash it gives ethylene oxide, 

CH„ 

I >o. 

CH 2 

a-Monochlorhydrin (3-chlor-i ,2 -propanediol), 

CH 2 C1 • CHOH • CH 2 OH, 

is prepared by treating glycerol with hydrochloric acid. It 
boils, with some decomposition, at 213 , without decomposi- 
tion at 1 39 under a pressure of 18 mm. 



CHLORAL 405 

s-Dichlorhydrin , ( 1 , 3-dichlor-2-propanol) , 
CH 2 C1CH0HCH 2 C1, 
is prepared by treating glycerol with sulphur chloride. 

C 3 H 8 3 +2S 2 C1 2 =C 3 H 6 C1 2 + 2HC1+S0 2 + 3S. 

It is also formed by treating glycerol with hydrochloric 
acid. It boils at 17 6°. It is oxidized to chloracetic acid 
by the chromic acid mixture, and gives epichlorhydrin, 

CH 2 C1CH — Crl 2 , 
\ / 
O 

when treated with solid sodium hydroxide. 

Trichlorhydrin (1,2,3-trichlorpropane) is prepared by treat- 
ing dichlorhydrin with phosphorous pentachloride. It boils 
at 158 . 

2,4,6-Tribromphenol, C 6 H 2 Br 3 OH, is formed by the direct 
bromination of phenol. It melts at 95 , and sublimes easily. 

Chloral (trichloracetaldehyde), 

cci 3 c( H , 

can be prepared by the chlorination of aldehyde in the pres- 
ence of considerable water, or of water and calcium Carbon- 
ate, the latter to neutralize the hydrochloric acid, and prevent 
its condensing effect on the aldehyde. Practically, chloral is 
prepared by the action of chlorine upon ethyl alcohol, the 
final product of the action being chloral alcohol ate, 

CC1 3 CH<°J H 5. 

This is then mixed with concentrated sulphuric acid and 
distilled. The crude chloral is combined with water to chlo- 



406 ORGANIC CHEMISTRY. 

ral hydrate, CC1 3 CH(0H) 2 , which is finally crystallized 
from carbon bisulphide, chloroform, ligroin, or turpentine. 
The reactions are probably as follows : 

*° 

Aldehyde 



CH 3 CH 2 OH + 2Cl = CH 3 C ( TT + 2 HC1, 



y/ 



O / OC 2 H 



CH 8 -C r „ + 2 C 2 H 5 OH = CH 3 -C _OC 2 H 5 +H 2 0. 
XH \H 

Acetal (p. 285). 

CH 8 CH(OC 2 H 5 ) 2 + 6Cl = CCl 8 CH(OC 2 H 5 ) 2 +3HCl. 

Trichloracetal. 

CC1 3 CH(0C 2 H 5 ) 2 + HC1 = CC1 8 CH < ^ Hs + C 2 H 5 C1. 

Chloral alcoholate. 

or h //O 

CC1 3 CH< 0H 2 5 +H 2 S0 4 =CCl 3 C( H + C 2 H 5 HS0 4 +H 2 0. 

Chloral. 

Chloral boils at 9 7. 7 , and has a specific gravity of 1.5 121 

20° 

at —5- • It does not, itself, mix with water ; but it combines 
4 

with it to form chloral hydrate, CC1 3 CH(0H) 2 , consider- 
able heat being evolved in the reaction. Chloral hydrate 
melts at 57 and is easily soluble in water and alcohols. 
The vapor density of chloral hydrate shows that, in the 
gaseous state, it is decomposed into chloral and water. 
Its magnetic molecular rotation (p. 49) at 54.6 , however, 
proves that, at that temperature, the water is chemically 
combined. (Perkin, J. Chem. Soc. (London), 51, 809.) It 
illustrates, again, the retention of two hydroxyl groups by a 
carbon atom which is combined with a strongly negative 
group. 

Chloral hydrate is taken in doses of 1.5 to 5 grams to pro- 
duce sleep. It is also used for the preparation of pure 
chloroform. 



MONOCHLORACETIC ACID. 407 

Chloral exhibits the usual characteristics of an aldehyde : 
nitric acid oxidizes it to trichloracetic acid ; it combines with 
ammonia, and with acid potassium sulphite ; with hydroxyl- 
amine it forms an addition product, 

CC, 3 CH<^ 0H 

as well as the oxime, 

ccic' N0H 

3 \ H 

This addition product is of especial interest as indicating 
that in all cases similar addition products are the first step 
in the formation of oximes. Also, the possibility of its ex- 
istence evidently depends on the same property of the mole- 
cule as that which makes it possible for two hydroxyl groups 
to remain combined with the same carbon atom in chloral 
hydrate. 

Monochloracetic Acid, CH 2 C1C0 2 H, is prepared by the 
chlorination of acetic acid, acetic anhydride, or acetyl chlo- 
ride in the direct sunlight, some iodine being added to aid 
the reaction. The acid melts at 63 , and boils at i8^°-i8j°. 
It is deliquescent, and very easily soluble in water. It raises 
blisters on the skin. Monochloracetic acid is used in the 
laboratory for the preparation of malonic ester, 

P H .C0 2 C 2 H 5 
C0 2 C 2 H 5 



cyanacetic ester, 

CH 2 < 



CQ 2 C 2 Il5 
"CN ' 



glycocoll (aminoacetic acid), 

CH 2 < C °* H 



NH 8 



408 ORGANIC CHEMISTRY, 

gly colic acid,. COoH 

CH 2<0H , 

and other compounds. It is now manufactured on a very 
large scale for use in making artificial indigo (Ber. 33, 
LXXXII. ; Address of H. Brunck, at the opening of the Hof- 
mann House in Berlin). 

Dichloracetic Acid, CHC1 2 C0 2 H, can be obtained by the 
chlorination of acetic acid, but is most easily prepared by 
boiling chloral hydrate with a solution of potassium cyanide 
or potassium ferrocyanide. 

CC1 3 CH(0H) 2 4-KCN = CHC1 2 C0 2 H + KC1+HCN. 

Practically, one part of the molecule is oxidized by the 
reduction of the other part. Dichloracetic acid melts at — 4 , 
and boils at 189°-! 9 1°. 

Trichloracetic Acid, CCl 3 COOH, can be prepared by the 
chlorination of acetic acid, but is most easily obtained by the 
oxidation of chloral hydrate with fuming nitric acid, or with 
potassium permanganate. Trichloracetic acid melts at 55 , 
and boils at 195 . When its solution is boiled with alkalies, 
it decomposes into chloroform and carbon dioxide. The 
decomposition is closely analogous to the "ketonic " decompo- 
sition of acetoacetic acid, and is evidently due to the same 
cause, — an instability of the molecule caused by the pres- 
ence of a negative group. 

Historical Importance of Trichloracetic Acid. — The discov- 
ery of trichloracetic acid by Dumas (Ann. Chem. (Liebig), 
32, 101, (1839)), is of unusual historical interest. It demon- 
strated that the " positive " hydrogen atoms of acetic acid 
can be replaced by " negative " chlorine atoms, while the 
general characteristics of the compound as an acid remain 
unchanged. Such a result is entirely inconsistent with the 



IODOPROPIONIC ACID. 409 

dualistic electrochemical theory of chemical compounds which 
was at that time generally accepted. The discussion which 
followed finally led to the overthrow of that theory and to a 
return to a unitary view of chemical compounds. 1 * 

Dissociation Constants of the Chloracetic Acids. — While the 
notion that hydrogen can be replaced by chlorine without 
changing the general properties of a compound was of the 
greatest importance at the time, it must not be overlooked 
that the substitution produces a great change in some of the 
properties of trichloracetic acid. While methane is formed 
from acetic acid only by heating it with sodium hydroxide to 
a comparatively high temperature, trichloracetic acid gives 
chloroform when simply boiled with caustic potash or even 
with water. The difference is still more clearly seen in the 
" strength " of the acids. The values of K (p. 54) are : 

Acetic acid 0.00180 

Monochloracetic acid . . . . 0.155 

Dichloracetic acid 5.17 

Trichloracetic acid . . . . . 121. 

a-Brompropionic Acid, CH 3 CHBrC0 2 H, is prepared by the 
direct bromination of propionyl bromide, CH 3 CH 2 COBr. It 
melts at 2 4. 5 °, and boils at 205.5 . An aqueous solution 
of its potassium salt gives lactic acid and potassium bromide 
on standing. 

/3-Iodopropionic Acid, CHJCH 2 C0 2 H, is prepared by heat- 
ing a mixture of acrylic acid and concentrated hydriodic acid 
to 130 . It melts at 8 2 . 

* One of the brightest bits of sarcastic writing in chemical literature appeared, 
under the pseudonym of S. C. H. Windier, from the pen of Wohler {Ann. d. Chem. 
{Liebig), 33, 308) during this discussion. It is well to remember, however, that both in 
this case and in the somewhat similar article by Liebig on fermentation {Ann. d. Chem. 
{Liebig), 29, 100 (1839)), the views which appeared to the writers as ridiculous are, after 
all, essentially true. 



4IO ORGANIC CHEMISTRY. 

Orthobrombenzoic Acid, 

C0 2 H i 
C6Hl< Br 2' 

can be prepared by oxidizing orthobromtoluene with nitric 
acid or with potassium permanganate. (Why not with chro- 
mic acid?) It melts at 148 . 

Metabrombenzoic Acid is prepared by heating benzoic acid 
with bromine and water in a sealed tube. It melts at 155°. 

Parabrombenzoic Acid, may be prepared by oxidizing para- 
bromtoluene with the chromic acid mixture. It melts at 

251°. 

The three brombenzoic acids may also be prepared from 
the corresponding amino acids by Sandmeyer's reaction 
(p. 460). 

Laboratory Exercises. 

Preparation of the following compounds : 

1. Ethyl bromide. 

2. Ethylene bromide. 

3. Isopropyl iodide. 

4. Amyl bromide. 

5. p-Dibrombenzene. 

6. Benzyl bromide. 

7. p-Bromtoluene from toluene and from p-toluidine. 

8. Chloroform. 

9. a-Brombutyric acid. 

10. Trichloracetic acid. 

11. Pinene hydrochloride. 



SALTS OF THE NITROPARAFFINS. 411 



CHAPTER XIX. 
NITRO COMPOUNDS. 

Ethyl Nitrite, C 2 H 5 0-NO. — When a solution of so- 
dium nitrite containing alcohol is dropped into dilute sul- 
phuric acid, ethyl nitrite is formed. It is a very volatile 
liquid, which boils at 17 . It is decomposed by alkalies 
very easily with the formation of alcohol and a metallic 
nitrite, and has all of the properties of a true ester. It is 
supposed to have the structure given above. 

Nitroethane, C 2 H 5 N0 2 . — When silver nitrite is treated 
with ethyl iodide, a mixture of ethyl nitrite and an isomeric 
compound of totally different properties is formed. This 
isomeric compound is nitroethane. It boils at ii4°-ii5°. 
It forms characteristic salts with metals, of which the sodium 
salt, C 2 H 4 N0 2 Na, is an illustration. By reduction it gives 
ethyl amine, C 2 H 5 NH 2 , a fact which indicates that the nitro 
group is attached to the ethyl by means of the nitrogen 
atom. When heated with hydrochloric acid it gives hydroxyl- 
amine hydrochloride and acetic acid, 

CH 3 CH 2 N0 2 + HC1 + H 2 = CH 3 C0 2 H + NH 2 O H-HC1. 

Salts of the Nitroparaffins. Pseudo Acids. — Primary and 
secondary nitroparaffins form salts similar to the sodium 
nitroethane mentioned above ; tertiary nitro compounds (e.g., 
tertiary nitrobutane (CH 3 ) 3 C ■ N0 2 ) do not form such com- 
pounds. Some authors have supposed that the metal is com- 



412 ORGAN IC CHEMISTRY, 

bined with carbon in these bodies, and formulate sodium 
nitroethane, as N0 2 

CH3CH< Na * 
The facts just given indicate that, while the free nitro com- 
pound may, probably, have the structure CH 3 — CH 2 — N0 2 , 
the salts are derived from the tautomeric form, and have 
the structure, CHs _CH = <[J H - 

Compounds of this type are called " pseudo " acids, because 
the free nitro compound is not a true acid at all. Hantzsch 
has shown (Ber. d. chem. Ges. 32, 575), by a study of the 
electrical conductivity and the reactions with ferric chloride, 
that when the nitro paraffin (as nitroethane for instance) is 
liberated from a solution of its salt the isonitro form, 

//° 
CH 3 — CH = N x q H > 

is at first obtained ; but the decreasing conductivity proves 
that it slowly passes into the true nitro form, 
CH 3 -CH 2 -N0 2 . 
The formation of aldehydes and ketones by the decompo- 
sition of salts of the nitroparaffins with acids also points 
very strongly to the constitution given above for those salts 
(Nef, Ann. d. Chem. (Liebig), 280, 266) : 

2R-CH = N-ONa+2HCl 

II 
O 

Sodium salt of a primary JsJ 

^compound. =2 R_CH = 0+|| >+2NaCl + H 2 0; 

N 

2^>C = N-ONa+2HCl 

R II 

O 

Sodium salt of a secondary x> N" 

nitrocompound. = 2 ^ > C = O + II X + 2NaCl + H 2 0. 

Jx. / 



NITROBENZENE. 413 

Nitro compounds of some of the paraffins and of some 
cyclic hydrocarbons have been prepared by direct treatment 
with nitric acid ; but, while the method is general and of 
very great importance for aromatic compounds, it has been 
comparatively little used for aliphatic and alicyclic bodies. 
In the aromatic series strong nitric acid, or a mixture of 
nitric and sulphuric acids, is used. For the nitration of 
aliphatic compounds, or of homologues of benzene in the 
side chain, dilute nitric acid seems to be more suitable. 
(Konowalow, Ber. d. Chem. Ges. 28, 1852, and 29, 2199 ; 
Worstall, however, obtained nitro paraffins by using a 
stronger acid, Avi. Chem.J. 20, 202). 

Nitrobenzene, C 6 H 5 N0 2 , is prepared, commercially, by 
allowing benzene to run into a mixture of nitric and con- 
centrated sulphuric acids. According to the proportions 
used and the temperature at which the nitration takes place, 
mononitrobenzene or m-dinitrobenzene can be prepared : 

C 6 H 6 + HN0 3 = C 6 H 5 N0 2 + H 2 0. 

Nitrobenzene is a yellow liquid, which solidifies at a low 
temperature, and melts at 3 . It boils at 210 . Nitroben- 
zene has a pleasant odor resembling that of oil of bitter 
almonds. It is used in perfumery as "essence of mirbane." 
It is poisonous. It is quite easily volatile with water vapor, 
readily soluble in alcohol and benzene, only very slightly 
soluble in water. It can be easily reduced to aniline, 
C 6 H 5 NH 2 , by a variety of reducing agents. 

In the nitration of derivatives of benzene the same laws 
hold as in the preparation of halogen compounds. The 
nitro group enters ortho or para to CH 3 , C 2 H 5 , OH, NH 2 , 
CI, Br, or I and meta to C0 2 H, S0 3 H, CHO, CN, CC1 3 , or 
NO,. 



414 ORGANIC CHEMISTRY. 

C 6 H 4 < 



Metadinitrobenzene, ^ TX ^ N0 2 



. N0 2 3' 

is readily prepared by the direct nitration of benzene, and 
its formation is the easiest method of identifying small 
amounts of benzene. It melts at 91 , and boils at 297 . 

s-Trinitrobenzene, / N0 2 1 

C 6 H 3 -N0 2 3, 
\N0 2 5 

is prepared by heating m-dinitrobenzene for three days at 
8o°-i2o° with a mixture of fuming sulphuric acid and nitric 
acid. It crystallizes in leaflets which melt at i2i°-i2 2°. 

o-Nitrotoluene is formed, together with the para com- 
pound and a trace of the meta derivative, by the direct 
nitration of toluene. It is prepared pure, by elimination of 
the amino (NH 2 ) group from orthonitroparatoluidine, 

/CH 3 1 
C 6 H 3 -N0 9 2. 
\ NH a 4 

The latter compound is prepared by the nitration of para- 
toluidine, 

TH^ CH3 1 
^ 6 4< NH 2 4 

in the presence of a large amount of sulphuric acid, the com- 
bination of the sulphuric acid with the amino group giving to 
it, apparently, the effect of a negative group in the orienta- 
tion of the nitro group. Orthonitrotoluene melts at — 10.5 , 
and boils at 21 8°. 

m-Nitrotoluene is prepared by the elimination of the amino 
group, from metanitroparatoluidine, 

/CH 3 1 

C 6 H 3 -N0 2 3. 

\NH 2 4 



NI TROX YLENES. 4 1 5 

This compound is prepared by the nitration of p-acettoluid, 

Le 4< NHC 2 H 3 0' 

and subsequent saponification of the nitroacettoluid formed. 
Metanitrotoluene melts at -f-i6°, and boils at 23o°-23i°. 

p-Nitrotoluene is prepared by the direct nitration of 
toluene. The difference in boiling point between the ortho 
and para compounds is enough in this case, so that they 
can be partly separated by frictional distillation. The para 
compound can then be, purified by crystallization from 
alcohol. It melts at 54 , and boils at 2 3 8°. 

The three nitrotoluenes give, by reduction, three to- 
luidines, CH 3 

w< nh; 

Phenylnitromethane, C 6 H 5 CH 2 N0 2 , can be prepared by 
heating toluene with dilute nitric acid (1.12) under pressure. 
{Ber. 28, 1857; 29, 699.) It boils at 225 — 227 , and has 
the characteristics of an aliphatic nitro compound, giving a 
sodium salt which is difficultly soluble in alcohol, and 
yielding hydroxylamine and benzoic acid when heated with 
hydrochloric acid. Tin and hydrochloric acid reduce it to 
benzyl amifie, C 6 H 5 CH 2 NH 2 . 



Nitroxylenes. — The six nitroxylenes indicated by the the- 
ory are all known. The compounds chiefly formed by the 
nitration of commercial xylene are the asymmet?'ic nitrometa- 


xyfene, 

/CH 3 

C 6 H 3 — CH 3 

\N0 2 


1 
4 


and niiroparaxylene , / CH 3 

C 6 H 3 -N0 2 

\CH 3 


1 

2. 
4 



41 6 ORGANIC CHEMISTRY. 

The nitroxylenes give, by reduction, xylidines, 

tfid3< NH 2 * 
a-Nitronaphthalene, N0 



CO 



is formed by the direct nitration of naphthalene. It melts at 
6i°, and boils at 304°. 

o-Nitrophenol, 

U±l4< N0 2 2' 

is formed by the direct nitration of phenol with nitric acid 
(1.34). The para compound is formed in smaller amount at 
the same time. After separating from the nitric acid, the 
ortho compound passes over, on distillation with water vapor, 
while the para compound remains behind. Orthonitrophenol 
melts at 44.27 , and boils at 214 . 

m-Nitrophenol is prepared from metanitraniline, 

N0 2 1 
NH 2 3' 



c 6 h 4 <: 



by means of the diazo reaction (p. 460). It melts at 96 , and 
boils at 1 9 4 under a pressure of 70 mm. 

p-Nitrophenol is prepared by the direct nitration of phenol 
(see above). It melts at 114 , and boils with slight decom- 
position. 

o-Nitrobenzoic Acid, 

C0 2 H 1 

CeH4< N0 2 2' 



NJTROCINNAMIC ACID. 41J 

is prepared by the oxidation of orthonitrotoluene, 

CeH4< N0 2 ' 

by means of potassium permanganate. It melts at 147 , and 
has an intensely sweet taste. It gives anthranilic acid, 

C0 2 H 1 
te 4< NH 2 2' 
by reduction. 

m-Nitrobenzoic Acid. — When benzoic acid is nitrated 
directly by use of concentrated sulphuric acid and potas- 
sium nitrate, a mixture consisting of about 75 per cent of the 
meta, 22 per cent of the ortho, and 2\ per cent of the para- 
nitrobenzoic acid is formed. The metanitrobenzoic acid 
melts at I4i°-i42°. 

p-Nitrobenzoic Acid is prepared by oxidizing paranitrotol- 
uene with the chromic acid mixture, or, better, with potas- 
sium permanganate. It melts at 2 3 8°. 

Dissociation Constants of Nitrobenzoic Acids. — The elec- 
trical conductivity constants of the three nitrobenzoic acids 

are : 

o-Nitrobenzoic acid K = 0.616. 

m-Nitrobenzoic acid .' K = 0.0345. 

p-Nitrobenzoic acid K = 0.0396. 

Benzoic acid . K = 0.0060. 

The effect of the nitro group on the strength of the acid, 
especially when in the ortho position, is very noticeable. 

o-Nitrocinnamic Acid, 

r „ CH = CHC0 2 H 1 
C ' H<< N0 2 

is prepared, together with the para compound, by the care- 



41 8 ORGANIC CHEMISTRY. 

ful nitration of cinnamic acid. It may also be prepared by 
Perkin's synthesis (p. 244) from o-nitrobenzaldehyde, 

rH CHO 

sodium acetate and acetic anhydride. It melts at 240 . 
Under proper conditions it gives orthonitrophenyldibrom- 
propionic acid, 

_ __ CHBrCHBrC0 2 H 

CeH4< NO, 



This, with a cold solution of sodium hydroxide, gives o-nitro- 
phenylpropiolic acid, 

C 6 H 4 < 



C = CC0 2 H 



N0 2 

Orthonitrophenylpropiolic acid decomposes suddenly when 
heated to i55°-i56°. It also decomposes on boiling its 
aqueous solution, another illustration of instability caused by 
the presence of negative groups. It gives, by the decompo- 
sition, phenylacetylene, C 6 H 5 C = CH, and carbon dioxide. 
When heated with alkalies it gives isatin : 

C 6 H 4 <^ C - C ° 2H = C 6 H 4 ( C ^)c-OH+CO, 

Isatin. 

The reduction of nitrophenylpropiolic acid to indigo has 
been considered (p. 247). 

Nitrourea, 

NHN0 2 
CO< NH 2 ' 

is prepared by dissolving nitrate of urea, 

NH 2 HNO s 
CO< NH 2 



LABORATORY EXERCISES. 419 

in ice-cold concentrated sulphuric acid. It can be reduced 
to semicarbazine (often called semicarbazide), 

NH-NH 2 
• CO< NH 2 

by means of zinc dust and hydrochloric acid. Semicarbazine 
has proved very useful as a reagent in working with alde- 
hydes and ketones (p. 179). It is kept in the form of the 
hydrochloride, 

C0< NHNH 9 HC1 

which crystallizes in prisms that melt at 173 . 



NH 2 



Laboratory Exercises. 
Preparation of the following compounds : 

1. Metadinitrobenzene. 

2. Ortho and p-nitrotoluenes, and their oxidation to nitro ben- 

zoic acids. 

3. m-Nitrotoluene. 

4. o-Nitro-p-toluidine. 

5. a-Nitronaphthalene. 

6. m-Nitrobenzoic acid. 

7. Semicarbazine hydrochloride. 



420 ORGANIC CHEMISTRY. 



CHAPTER XX. 

AMINES. 

Amines or amino * compounds may be considered either 
as ammonia in which one or more hydrogen atoms have 
been replaced by a hydrocarbon radical, or as hydrocarbons, 
or carbon compounds, in which hydrogen has been replaced 
by the amino (NH 2 ) group. Thus methyl amine may be 
written either as 



/CE 

-H 

\H 



/NH 2 



or, C X !? 

\H 



Amines are distinguished as primary, seco?idary, or tertiary, 
according as one, two, or three of the hydrogen atoms in 
ammonia are replaced. There are also qaartemary ammo- 
nium bases, in which the four hydrogen atoms of the ammo- 
nium group have been replaced. Thus we have : 

Methyl amine (primary) CH 3 NH 2 

Dimethyl amine (secondary) (CH 3 ) 2 NH 

Trimethyl amine (tertiary) (CH 3 ) 3 N 

Tetramethyl ammonium hydroxide . . . (CH 3 ) 4 NOH 
(Quaternary ammonium base) 

Amines are prepared: 

i. By the action of halogen alkyls on ammonia. 

* For the distinction between amino and amido compounds see p. 289. 



AMINES. 421 

C 2 H 5 Br-f NH 3 = C 2 H 5 NH 2 HBr. 
C 2 H 5 Br-f C 2 H 5 NH 2 = (C 2 H 5 ) 2 NHHBr. 
C 2 H 5 Br + (C 2 H 5 ) 2 NH = (C 2 H 5 ) 8 NHBr. 
C 2 H 5 Br + (C 2 H 5 ) 3 N = (C 2 H 5 ) 4 NBr. 

The amines combine with acids to form ammonium salts, 
as ammonia itself does ; and these salts can be decomposed 
b) T alkalies with the liberation of the free amine, just as am- 
monium chloride is decomposed by sodium hydroxide or 
lime. 

The method just given is much less useful than might be 
expected, because of the formation of a mixture of primary, 
secondary, and tertiary amines, from which it is difficult to 
separate pure compounds. This is undoubtedly due to the 
fact that a portion of the salt of the amine at first formed is 
at once decomposed by the ammonia still present, and the 
resulting amine then combines with a second molecule of the 
alkyl halide, thus : 

C 2 H 5 Br + NH 8 = C 2 H 5 NH 2 HBr. 
C 8 H 5 NH 2 HBr+NH s = NH 4 Br + C 2 H 5 NH 2 
C a H 6 NH 2 + C 2 H 6 Br = (C 2 H 5 ) 2 NHHBr. 

2. By the reduction of nitro compounds : 

C 6 H 3 N0 2 + 6 H = C 6 H 5 NH 2 -f-2 H 2 0. 

Nitrobenzene. Aniline. 

(Aminobenzene.) 

The aromatic nitro compounds are so easily prepared, and 
so readily reduced, that this method is of much greater im- 
portance than any other for the preparation of that class of 
bodies. The method applies equally, however, to aliphatic 
and alicyclic nitro compounds. 

A great variety of reducing agents are used in special 
cases. For general laboratory use, and especially for the 



422 ORGANIC CHEMISTRY, 

complete reduction of several nitro groups, tin and hydro- 
chloric acid is, probaby, most common. For technical use, 
iron and hydrochloric or acetic acid are very important. For 
acids, and for partial reduction when several nitro groups 
are present, ammonium sulphide is often useful. 

3. By the reduction of cyanides, oximes, and hydrazones : 
C 6 H 5 CH 2 CN + 4 H = C 6 H 5 CH 2 CH 2 NH 2 

Benzyl cyanide. w-Phenyl ethyl amine. 



chI> c = n -° h+ 4 h =ch: 

Acetoxime. • Isopropyl amine. 



>C = N-OH + 4 H=^ TT 3 >CHNH 2 + H 2 



C 6 H 5 CH = NNHC 6 H 6 + 4H = C 6 H 5 CH 2 NH 2 + C 6 H 5 NH 2 

Phenyl hydrazone of benzaldehyde. Benzyl amine. Aniline. 

Sodium amalgam, and absolute alcohol with sodium are 
the most common reducing agents for these compounds. 

4. By treating an isocyanate with potassium hydroxide, 

C 2 H 5 N = C = O + 2 KOH = C 2 H 5 NH 2 + K 2 C0 3 . 

Ethyl isocyanate. Ethyl amine. 

This method is of especial interest because it led to the 
preparation of the first amine. (Wurtz, Ann. d. Chem., 
(Liehig), 71, 330 ; 76, 325.) 

5. By treating an acid amide with bromine and sodium hy- 
droxide, or with sodium hypobromite (Hofmann's reaction) : 

CH s C-NH 2 +Br 2 + 4 NaOH = CH 3 NH 2 +2NaBr+Na 2 C0 3 

Acetamide. Methyl amine. 4-2HO 

The reaction, superficially considered, consists simply in 
the removal of carbonyl (CO), but it is probably closely 
associated with the preceding method, and depends on the 
following steps : 



PROPERTIES OF THE AMINES. 423 

//O /y O 

CH 3 C-NH 2 -fBr 2 =CH 3 -C-NHBr-f-HBr 

Bromacetamide. 

. //O /O-Na 

CH 3 C - NHBr + NaOH = H 2 + CH 3 C = NBr 

->NaBr + CH 3 C-N->CH 3 N = C = 0-f-2NaOH = 

CH 3 NH 2 +Na 2 C0 3 . 

6. Treatment of potassium phthalimide with a halogen 
alkyl followed by a saponification of the resulting alkyl 
phthalimide : 



C 6 H 4 <^>NK + C a H 5 I = C G H 4 <^>NC a H B +KI 



CO CO 

C0 >NK+C 2 H 5 I = C 6 H 4 <^ 

Potassium phthalimide. Ethyl phthalimide. 

CO 
C 6 H 4 < > NC 2 H 5 + HC1 + 2 H 2 = C 6 H 4 (C0 2 H) 2 

+ C 2 H 5 NH 2 HC1 

This method, which resembles the first above, has the 
advantage of giving pure primary amines. It depends, 
partly, on the fact that imides of the acids do not form 
quaternary compounds. 

Properties of the Amines. 

As derivatives of ammonia, and resembling it in general 
chemical properties, the amines combine with water to form 
bases,^ and with acids to form alkyl ammonium salts. Just 
as, however, ammonium hydroxide exists only in solution, so 
only the quaternary ammonium hydroxides can exist other- 
wise than in solution. 

The " strength " of the alkyl ammonium bases varies 

* In the light of our present knowledge, the common statement that ammonia and 
the amines are themselves bases cannot be considered as true. It is, however, often 
convenient to speak of the amines as bases, and the common usage will be sometimes 
followed here. 



424 ORGANIC CHEMISTRY. 

greatly. It is most accurately measured by means of the 
electrical conductivity of their aqueous solutions.* The fol- 
lowing values may be taken as typical illustrations : 

For ammonia, NH^OH K = 0.0023 

For ethyl amine, C 2 H 5 NH 3 OH K = 0.056 

For diethyl amine, (C 2 H 5 ) 2 NH 2 OH .... K = 0.126 

For triethyl amine, (C 2 H 5 ) 3 NHOH K = o.o64 

Tetrethyl ammonium hydroxide, (C 2 H 5 ) 4 NOH, is disso- 
ciated to the extent of 88 per cent in a solution where 
v = 16 ; that is, it belongs to the very strong bases. 

For allyl amine, C,H,NH 3 OH K = 0.0057 

For benzyl amine/ C f H-CH s NH 3 OH .... K = o.oo2 4 

For piperidine, CH 2 < ^ 2 _ ^ R 2 > NH 2 OH K = 0.158 

(See Bredig, Zeit. f. Phys. Ch. 13, 289). 

The difference in " strength " of the bases is also illus- 
trated qualitatively by their conduct toward weak acids, 
especially carbonic and acetic acids, and by the conduct of 
their salts toward water. The alicyclic amines (as amino- 

CH 2 -CH 2 
cydofieiitane, | > CHNH 2 , and aliphatic amines (as 

CH 2 — CH 2 
ethyl amine, CH 3 CH 2 NH 2 ) form well-defined carbonates and 
very stable salts. They can be titrated by means of stand- 
ard acids with the use of rosolic acid, litmus, or methyl 

* Strictly speaking, the " strength " of a base should represent the relation between 
the amounts of the hydroxide and of the ions into which it dissociates. Since, how- 
ever, larger or smaller quantities of the amine uncombined with water are also present 
and this fact has not been considered in the calculation of the constants, these may be 
quite misleading. Thus it is altogether probable that the very much greater apparent 
"strength" of the tetrethyl ammonium hydroxide is due to the fact that it does not 
dissociate into amine and water, while the other bases do this to a very large extent. 
The degree of dissociation into amine and water is also quite independent of the de- 
gree of ionization of the hydroxide. See Hantzsch and Sebaldt, Zeit. f. ph. Chem. 
30, 258 ; Hantzsch and KdL\b,Ber. d. chem. Ges. 32, 3109; and Frenzel, Zeit, anorg. 
Chem. 32, 319. 



PROPERTIES OF THE AMINES 425 

orange as indicators, in the same manner as ammonia. The 
aromatic amines, in which the amino group is combined with 
the nucleus, on the other hand, form no carbonates, and, 
while some of them (as aniline C 6 H 5 NH 2 ) form stable salts 
with strong acids, solutions of such salts react acid toward 
litmus and other indicators, even in the presence of a large 
excess of the amine. It is evident that in such cases the 
amount of the base (C 6 H 5 NH 3 OH) which can exist in an 
aqueous solution is vanishingly small. When the negative 
character of the phenyl group is enforced by the presence of 
nitro groups or other negative atoms or groups (as in o-nitran- 

iline, CH 4 <^ T ^ 2 j, the salts often become so unstable 
6 N0 2 2/ 

that they are decomposed by water, with precipitation of the 

7 NH 2 

base. In the case of dinitraniline, C 6 H 3 — N0 2 , no salts at 

X N0 2 

all have been prepared. There are, therefore, all degrees of 

" strength," from the quaternary ammonium bases (as tetra- 

ethyl ammonium hydroxide (C 2 H 5 ) 4 NOH), which resembles 

the fixed alkalies, to dinitraniline and similar amines, which 

form no salts. Possibly a truer picture still is given by 

placing at the other extreme the imides (as phthalimide, 

CO 
C 6 H 4 < >NH), in which the hydrogen of the substituted 

ammonia has acquired distinctly acid properties, though this 
is probably due to a rearrangement to the form 

/ C-OH 
C 6 H ^ 

x co/ ' 

Effect of Nitrous Acid on Amines. — Closely parallel with 
the basic properties of the amines is the conduct of primary 
amines toward nitrous acid. The alicyclic amines generally, 



426 ORGANIC CHEMISTRY. 

and the aliphatic amines in some cases, form nitrites which 
are sufficiently stable to be crystallized, and which decompose 
but slowly on boiling their neutral or faintly alkaline solutions. 
The nitrites of aliphatic amines are usually unstable, and de- 
compose in a manner closely analogous to the decomposition 
of ammonium nitrite : 

NH 4 N0 2 = N 2 + HOH + H 2 ; 

C 2 H 5 NH 2 HN0 2 = N 2 + C 2 H 5 OH + H 2 0. 

The nitrites may also decompose with the formation of 
unsaturated hydrocarbons : 
CH S 
CH 3 

Isopropyl ammonium nitrite. Propylene. 



>CHNH 2 HN0 2 = CH 8 CH = CH 2 + N 2 -t-2H a O. 



Aromatic amines do not, apparently, form nitrites, but give 
diazo compounds, which will be considered later (p. 456). 
Diazo compounds may be decomposed with water, giving 
phenols, and may be considered as an intermediate step in 
the reaction above, which gives an alcohol. This reaction, 
in connection with others which have been considered, makes 
it possible to pass from an alcohol to a homologous alcohol 
containing one more carbon atom, thus : 

CH 3 CH 2 OH->CH 3 CH 2 Br->CH 3 CH 2 CN 

^>CH 3 CH 2 CH 2 NH 2 ^>CH 3 CH 2 CH 2 OH. 

Nitrosamines. — If a salt or an acid solution of a second- 
ary amine is treated with nitrous acid, or with sodium nitrite, 
a nitrosamine is formed. 

(C 2 H 5 ) 2 NHHC1 + NaN0 2 = (C 2 H 5 ) 2 NNO + H 2 + NaCl. 

Diethylnitrosamin e. 

The aliphatic nitrosamines are usually yellow liquids, 
which can be distilled without decomposition, if not of too 



FORMATION OF ISOCYANIDES OR ISON IT RILES. 427 

high molecular weight, and are volatile with water vapor. 
As they are decomposed by concentrated hydrochloric acid, 
these properties furnish a means of separating secondary 
aliphatic amines from primary and tertiary amines, and of 
preparing them in pure condition. 

(C 2 H 5 ) 2 NNO + HC1 + H 2 = (C 2 H 5 ) 2 NHHC1 + HN0 2 . 

Nitrosamines may also be prepared from secondary aro- 
matic amines. These readily undergo a molecular rearrange- 
ment by which the nitroso group is transferred to the benzene 
nucleus. 

(C 6 H 5 ) 2 NNO -> C 6 H 4 < N 



L 5 

NO 

Nitrosodiphenyl amine. p-Nitrosophenyl aniline. 



If a nitrosamine is mixed with phenol and some concen- 
trated sulphuric acid added, on dilution with water, and 
neutralization with caustic potash or soda, a blue color is 
obtained. This is known as " Liebermann's reaction," and 
is useful for the qualitative detection of secondary amines. 
Nitrosophenol is probably formed by the reaction, and this 
condenses with more of the phenol, under the influence of 
the concentrated sulphuric acid, giving a compound which 
is red in an acid and blue in an alkaline solution. 

Tertiary amines do mot react readily with nitrous acid, but 
may, in part, lose one alkyl group and give secondary nitros- 
amines. 

Formation of Isocyanides or Isonitriles. — Primary amines 
react with chloroform and caustic potash to form isocyanides : 

C 2 H 5 NH 2 +CHCl 3 +3KOH = C 2 H 5 N = C + 3 KC1 + 3 H 2 0. 

The isocyanides can be easily recognized by their execrable 
odor, and the reaction is useful to distinguish primary from 
secondary and tertiary amines. 



428 ORGANIC CHEMISTRY. 

Primary and secondary amines react readily with phenyl 
sulphonic chloride in the presence of caustic soda. (Schotten- 
Baumann reaction, p. 282.) 

C 2 H 5 NH 2 +C 6 H 5 S0 2 Cl+NaOH 

= C 6 H 5 S0 2 NHC 2 H 5 +NaCl + H 2 0. 

Benzene sulphonic ethyl amide. 

(C 2 H 5 ) 2 NH + C 6 H 5 S0 2 C1 + NaOH 

= C 6 H 5 S0 2 N(C 2 H 5 ) 2 + NaCl + H 2 0. 

Benzene sulphonic diethyl amide. 

Because of the acid character of the hydrogen of the sul- 
phonamides, the compounds prepared from primary amines 
are usually soluble in alkalies, while those prepared from 
secondary amines are not. There are, however, some ex- 
ceptions, and an excess of the sulphonic chloride must be 
avoided in the preparation. (Hinsberg, Ber. d. chem. Ges. 
23, 2963 ; 33, 3526 ; Solonina, Central- Blatt, 1897, II., 
848). 

Tertiary amines do not react with phenyl sulphonchloride. 

Alkyl Thiocarbamic Acids. Isothiocyanates. — Primary and 
secondary amines combine directly with carbon bisulphide 
to form alkyl ammonium salts of alkyl thiocarbamic acid. 

Thiocarbamic acid is 

/NH 2 
C = S . 
\SH 

/ NHC 2 H 5 
2 C 2 H 5 NH 2 +CS 2 = C = S 

\SH-NH 2 C 2 H 5 

Ethyl ammonium ethyl 
thiocarbamate. 

When the thiocarbamate formed from a primary amine is 
warmed with ferric chloride, an isothiocyanate (mustard oil, 
p. 309) is formed, and can be recognized by its disagreeable 
odor. 



DIMETHYL AMINE. 429 



/ NHC 2 H 5 



C=S 

\SHNH 2 C 2 H 5 + 2 FeCl 3 
= C 2 H 5 -N = C = S + NH 2 C 2 H 5 -HCl + 2FeCl 2 + S + HCl. 

The reaction is closely related to the formation of ammonium 
thiocyanate, NH 4 -N = C = S, from carbon bisulphide and 
ammonia. 

Amines form compounds with chlorplatinic acid, H 2 PtCl 6 , 
and chlorauric acid, HAuCl 4 , which usually crystallize well, 
and serve excellently for purposes of identification and an- 
alysis. Ethyl ammonium chlorplatinate is, 

(C 2 H 5 NH 2 ) 2 H 2 PtCl 6 . 

Methyl Amine, CH 3 NH 2 , is most easily prepared from 
acetamide, CH 3 CONH 2 , by Hofmann's reaction. It may 
also be prepared by the reduction of chlorpicrin (nitrochlo- 
roform), CC1 3 N0 2 , or of hydrocyanic acid. It is a gas 
at ordinary temperatures, and is more soluble than ammonia 
in water. It has an ammoniacal, fishy odor. Its solution 
precipitates metallic hydroxides, and the hydroxides of nickel, 
cobalt, and cadmium do not dissolve in an excess, as they do 
in ammonia, while aluminium hydroxide dissolves in methyl 
ammonium hydroxide, but not in ammonium hydroxide. 
These phenomena are evidently dependent on the fact that 
methyl ammonium hydroxide is a stronger base than ammo- 
nium hydroxide. 

Methyl ammonium chloride is soluble in alcohol, while 
ammonium chloride is only very slightly soluble. The solu- 
bility of the chlorides and other salts of the amines in alco- 
hol is quite general, and is useful for purposes of separation. 

Dimethyl Amine, (CH 3 ) 2 NH, is most easily prepared from 

dimethyl aniline, C 6 H 5 N(CH 3 ) 2 , which is easily obtained 



43 O ORGANIC CHEMISTRY. 

from aniline, C 6 H 5 NH 2 , and methyl iodide or methyl chlo- 
ride. Dimethylaniline gives, with nitrous acid, p-nitroso- 
dimethylaniline, 

N(CH 3 ) 2 

and this, when boiled with a solution of sodium hydroxide, 
is decomposed, giving p-nitrosophenol and dimethylamine. 

C 6 H 4 < J^ CHs)2 + NaOH = C 6 H 4 <^ + NH(CH,) ! 

Sodium p-nitroso- 
phenolate. 

Dimethyl amine boils at 7. 2°. It mixes with water in all 
proportions. 

Trimethyl Amine, (CH 3 ) 3 N, is most easily prepared, in 
small quantities, by the distillation of tetramethyl ammonium 
hydroxide, 

(CH 3 ) 4 NOH = (CH 3 ) 3 N + CH3OH. 

Methyl amine, dimethyl amine, and trimethyl amine are 
all found in herring brine, and are also among the products 
obtained by the destructive distillation of the residues re- 
maining after preparing alcohol from the molasses of beet 
sugar. They are also prepared, commercially, by the inter- 
action of methyl chloride or methyl bromide and ammonia. 
On the other hand, since trimethyl amine gives methyl chlo- 
ride on heating with hydrochloric acid, the mixture of methyl 
amines from beet-sugar residues has been used for the 
commercial preparation of methyl chloride. 

(CH 3 ) 3 NHCl-f 3 HCl = 3 CH 3 Cl + NH 4 Cl. 

Trimethyl amine boils at 3.2 - 3 .8°. It has a penetrating, 
fishy odor. 



ETHYL AMINES. 43 1 

Tetramethyl Ammonium Iodide, (CH 3 ) 4 NI, is the final pro- 
duct of the action of methyl iodide on ammonia. It is diffi- 
cultly soluble in cold water, almost insoluble in alcohol, and 
can be easily purified by crystallization. As tetramethyl 
ammonium hydroxide cannot be distilled without decomposi- 
tion, it cannot be prepared by the action of alkalies on tetra- 
methyl ammonium iodide, or other similar salts. By treating a 
solution of the iodide with silver oxide, however, it can be ob- 
tained, and remains as a crystalline mass supposed to have 
the composition (CH 3 ) 4 NOH. At a time when the physical 
evidence of the existence of ammonium hydroxide in solution 
was not so well understood as it is at present, this, and the 
corresponding tetr ethyl ammonium hydroxide, (C 2 H 5 ) 4 NOH, 
were of especial interest as demonstrating the existence of 
ammonium hydroxide by analogy. The quaternary alkyl 
ammonium hydroxides are strong bases, resembling the fixed 
alkalies, potassium and sodium hydroxides, in their general 
properties. 

Ethyl Amines corresponding to the methyl amines are 
known. Also mixed amines, as dimethyl ethyl amine, 
(CH 3 ) 2 C 2 H 5 N, are known. 

At one time ammonium chloride and many other sub- 
stances were considered as " molecular compounds," and such 
formulae as NH 3 • HC1, were used, the idea being that the 
two molecules existed as such in ammonium chloride. Ac- 
cording to this conception dimethyldiethyl ammonium iodide 
should exist in two forms according to the method of prepa- 
ration, thus : 

(CH S ) 2 C 2 H 5 N + C 2 H 5 I = (CH 3 ) 2 C 2 H 5 N ■ C 2 H 5 I 
CH 3 (C 2 H 5 ) 2 N + CH 3 I = CH 3 (C 2 H 5 ) 2 N ■ CH 3 I. 
A careful study of the matter has shown that the products 



432 ORGANIC CHEMISTRY. 

formed by the two methods are identical. This can be 
readily explained only by assuming that the four groups and 
the halogen atom are combined directly with the nitrogen 
atom, and that the latter is quinquivalent. 

Asymmetry of Nitrogen Compounds. — Another question of 
considerable interest is, whether an asymmetry like that of car- 
bon (p. 137) is possible for nitrogen compounds. So long 
as only three atoms or groups are combined with a nitrogen 
atom asymmetric forms are impossible, if the centers of grav- 
ity of the groups lie in the same plane as the nitrogen atom. 
If the nitrogen atom lies in a different plane from that of the 
groups, as seems probable (p. 183), asymmetry is possible. 
No example of such asymmetry in the case of a compound 
having but three groups combined with the nitrogen atom 
has, however, been discovered. With five different groups, 
as in benzylphenylallylmethyl ammonium bromide, 

C 3 H 5 

C H I 
X^> N-Br, 



asymmetry has been actually established (Pope, J. Chem. 
Soc. [London] 75, 1127). 

Vinyl Amine, CH 2 = CHNH 2 , or more probably dimethylene 
imiiic, CH 

I >NH, 
CH 2 

is prepared by distilling bromethyl ammonium bromide, 
CH 2 BrCH 2 NH 2 HBr, with a strong solution of potassium 
hydroxide. It is insoluble in water, and boils at 55°-56°. 
It does not decolorize permanganate, a fact which almost 
certainly excludes the first formula. 



PENTAMETHYLENE DIAMINE. 433 

Vinyltrimethyl Ammonium Hydroxide, (neurine), C 2 H 3 N 
(CH 3 ) 3 OH, is a ptomaine # formed during the putrefaction 
of meat. It is very poisonous. It has also been prepared 
synthetically. Its platinum salt, (C 5 H 12 N 2 ) 2 PtCl 6 , crystallizes 
in octohedra which melt at 2i3°-2i4°. 

Ethylol Trimethyl Ammonium Hydroxide (choline), 

nypt^ C H 2 CH 2 OH 

is found in bile, the brain, the yolk of eggs, and other 
animal substances, combined with palmitic (oleic, stearic) 
and glycerol phosphoric acids, as lecithin. The lecithin 
containing only stearic acid and glycerol phosphoric acid, 
has the structure : 

CH 2 -0-C 18 H 35 

I 
CH - O - C 18 H 35 = C 44 H M N0 9 P. 

CH2_0_PO< -0-C 2 H 4 N(CH 3 ) 3 OH 

Choline is not poisonous. Choline and neurine have been 
mutually converted into each other. 

Pentamethylene Diamine (cadaverine), 

CH„-CH 9 NH 9 



CEL< 



CH 2 -CH 2 NH 2 



is another ptomaine which has been found among the pro- 
ducts of putrefaction of the human cadaver. It has also 
been prepared by the reduction of trimethylene cyanide, 

CH 2 CN 
2 < CH„CN' 

* Ptomaine is a name given to basic compounds formed during the decay of animal 
or vegetable substances, or in the living organism in some diseases. The ptomaines 
occasionally give color reactions resembling those of some poisonous vegetable 
alkaloids, and render the detection of the latter difficult in toxical analysis. 



434 ORGANIC CHEMISTRY. 

with absolute alcohol and sodium. It solidifies in a freezing 
mixture, boils at i78°-i79°, and has a specific gravity of 
0.8784 at 25 . It is not poisonous. 

Piperidine (hexahydropyridine or hexazane), 
CH 2 <^-CH 2>NHj 



is formed when cadaverine hydrochloride is distilled. 

PR CH 2 -CH 2 NH 2 HC1 
2 < CH 2 - CH 2 NH 2 HC1 

prr PTT 

= CH< 2 *>NH + HC1 + NH 4 C1. 

Ln 2 — ^xl 2 

It has also been prepared by the reduction of pyridine, 

CH / „ TT ^ N, with sodium and absolute alcohol. 

When piperine, which is found in black pepper, is boiled 
with alcoholic potash, piperidine and the potassium salt of 
piperic acid are formed : 

O *° 

CH 3 < o >C H 8 -CH = CH— CH = CHC-NC 6 H 10 +KOH 

= C 5 H n N + C 12 H 9 4 K 

Piperidine. Potassium piperate. 

Piperidine has an odor which recalls both that of ammonia 
and of pepper. It melts at— 17 , boils at 106 , and has a 
specific gravity of 0.8591 at 25 . It mixes with water in all 
proportions, and the solution is strongly alkaline. With 
nitrous acid it gives nitrosopiperidine, C 5 H 10 NNO. When 
heated with concentrated sulphuric acid to 300 , or with 
silver acetate and dilute acetic acid to 180 , it is oxidized to 
pyridine. 



coin in E. 435 

i. (») Methyl Piperidine, C 5 H 10 N — CH 3 , is formed when 
piperidine and methyl iodide are brought together. It is a 
liquid which boils at 107 , and has a specific gravity of 
0.821 at 15 . 

/3-Methyl Piperidine (a-pipecolin, 2-methyl hexazane), 

CH 2 — CH ^Hs 
CH2< CH 2 -CH 3 ) NH ' 

is prepared by the reduction of a-picoline {2-methyl pyridine) , 

N 

CH 2 



with sodium and absolute alcohol. It boils at 11 8°, and 
has a specific gravity of 0.8622 at o°. It is easily soluble 
in water, and has an odor like that of piperidine. 

^/-Coniine (2-propylpiperidine), 

CBL-CH -CH,CH,CH 3 
CH2< CH 2 -CH 2 >NH > 

is found in hemlock, and gives to it its poisonous properties. 
It has a peculiar penetrating odor, melts at 2.5 , boils 
at i66°-i66.5°, and has a specific gravity of 0.8625 at o°. 
[a] D = + 18.3 .. It is soluble in 90 parts of water, and itself 
dissolves about one-fourth of its weight of water. It is very 
poisonous. 

z'-Coniine, has been prepared synthetically by the reduc- 
tion of 2-allylpyridine, 



436 ORGANIC CHEMISTRY. 

N 

CH— CH=CH 2 



by means of sodium and absolute alcohol. It has been 
separated into its active constituents by means of the acid 
tartrate, C 8 H 17 N-H 2 C 4 H 4 6 . 

CH = CH 
Pyrrol, | > NH, is found in coal-tar, and in bone- 

CH = CH 

oil. It is formed by the distillation of ammonium saccha- 

mte ' CHOH - CHOH - C0 2 NH 4 

I 
CHOH-CHOH-C0 2 NH 4 

by passing diethyl amine, (C 2 H 5 ) 2 NH, through a red hot 
tube, and by reducing succinimide by distilling it with zinc 
dust. 

CH 2 -CO CH = CH 

| >NH + 2Zn= | >NH + 2 ZnO 

CH 2 -CO CH = CH 

Succinimide. Pyrrol. 

Pyrrol maybe considered as benzene in which — CH = 
CH— has been replaced by — NH — . It boils at i3o°-i3i°, 

21° 

and has a specific gravity of 0.967 at — -. Pyrrol is a very 

weak base, and has a strong tendency to polymerize. It 
forms pyrrol red, C 12 H 14 N 2 0, when warmed with dilute acids, 
and tripyrrol, (C 4 H 5 N) 3 , when its solution in ether is treated 
with hydrochloric acid gas and allowed to stand. 

One atom of hydrogen in pyrrol can be replaced by potas- 
sium, giving the compound, 



PYRIDINE. 437 

CH = CH 
I >NK. 

CH = CH 

This is decomposed by water, and pyrrol cannot, therefore, 
be considered as antacid (p. 221). 
Pyrrol may be reduced to pyrroline, 

CH-CH 2 

II >NH, 

CH-CH 2 

pyrrolidine ( pentazane ) , 

CH 2 -CH 2 

I >NH, 

CH 2 -CH 2 

and butyl amine, CH 3 CH 2 CH 2 CH 2 NH 2 . 

Pyridine, 

CH CH 

// 
CH 



CH 




/ 
CH 


\ 
CH 


II 
CH 


or 


II 
CH 


II , 
CH 






\ 


/ 



CH 

N N 

is found in coal-tar, and in bone-oil. It may be considered 
as benzene in which one CH group has been replaced by a 
nitrogen atom, and its formation by the destructive distilla- 
tion of animal matter is evidently analogous to the formation 
of benzene from vegetable matter. It is also formed by 
passing ethylallylamine, C 2 H 5 NHC 3 H 5 , over litharge heated 
to 4oo°-5oo°, and by warming piperidine (p. 434) with con- 
centrated sulphuric acid to 300 . 

Pyridine boils at 11 6°, and has a specific gravity of 
0.9778 at 2 5 . It mixes with water in all proportions, and 
is a very stable substance, resisting the action of even 
vigorous oxidizing agents. It is only a weak base. 



438 ORGANIC CHEMISTRY. 

Halogen substitution products, sulphonic acids, carboxyl, 
hydroxyl, and other derivatives of pyridine, are known. The 
same general principles of isomerism apply to them as in the 
case of benzene, with the differences caused by the presence 
of the nitrogen atom in the ring. Thus there are three 
monosubstitution products, six bisubstitution products with 
a single substituent, and ten with two different substituents. 

Picolines, QH 4 NCH 3 . There are three picolines, which 
are distinguished as a-, /?-, and /-picoline, or as i-, 2-, or 
3-met/iy /-pyridine. They are found in coal-tar and in bone- 
oil. They boil respectively at 129 , 143.5 , an( ^ I 43-5°- 

Lutidines, or Dimethyl Pyridines, and Ethyl Pyridines are 

known in considerable number. 

2, 4, 6-Trimethyl Pyridine (y-collidine) is prepared by dis- 
tilling a mixture of the potassium salt of collidine dicarboxylic 
acid, 

C0 2 H CH 3 



ch ; 



C0 2 H CH 3 

with calcium hydroxide. It boils at 171 — 172 , and has a 
specific gravity of 0.917 at 15 . 
Nicotine, 



N 




// \ 
CH CH 

C 10 H 14 N 2 or | || 

CH C - 


N-CH 3 
/ \ 
- CH CH 2 


^ / 
CH 


1 1 
CH 2 CH 2 



is found in tobacco, the amount varying from 0.6 to 8.0 per 
cent. When pure, it does not smell like tobacco. It boils 



ANILINE. 439 

20° 

at 247 , and has a specific gravity i.oiioi at — 5 * It 

mixes with water, alcohol, or ether in all proportions. 
Nicotine is laevorotatory [a] D = — 161.55 . In aqueous 
solutions the rotation is very much less, and varies with 
the concentration. Nicotine turns brown, and forms resinous 
products on exposure to the air. Chromic acid or potassium 
permanganate oxidize it to nicotinic acid {^-pyridine carboxylic 
acid). Nicotine is narcotic in its physiological action, and 
very poisonous. It forms salts with one or with two mole- 
cules of strong monobasic acids. In titrating, with rosolic 
acid as an indicator, the end point corresponds to the forma- 
tion of the salt, C 10 H 14 N 2 HC1. 

Aniline, C 6 H 5 NH 2 , was first obtained by distilling indigo, 
either alone or with caustic potash. The name is derived 
from anil, the Spanish name for indigo. Aniline is prepared 
by the reduction of nitrobenzene. In the laboratory, a great 
variety of reducing agents may be used, the most common 
being tin and hydrochloric acid, though this is liable to cause 
its contamination with chlorine compounds. For technical 
uses, aniline is manufactured in very large quantities by 
reducing nitrobenzene with iron and hydrochloric or acetic 
acid. 

C 6 H 5 N0 2 + 3 Fe + 6HCl = C 6 H 5 NH 2 -|-3FeCl 2 + 2H 2 0. 

In the presence of the chloride or acetate of iron the 
following reaction may also occur, and much less than the 
theoretical amount of acid is used : 

C 6 H 5 N0 2 +2Fe + 4 H 2 = C 6 H 5 NH 2 +2Fe(OH) 3 . 

When the reduction is complete, lime is added, and the 
aniline is distilled with water vapor. 

Aniline melts at —8°, boils at 183.7 , and has a specific 



440 ORGANIC CHEMISTRY. 

gravity of 1.024 at 16 . It is soluble in about 30 parts of 
water, while water, in turn, is soluble in about 20 parts of 
aniline. Aniline gives a purple color with an aqueous solu- 
tion of calcium hypochlorite, and a blue color with potassium 
pyrochromate. 

Aniline is a weak base (p. 425). With nitrous acid, in an 
acid solution, it gives dlazobenzene (p. 456). In both re- 
spects it differs from the aliphatic and alicyclic amines. 

Oxidation with chromic acid converts it partly into 

quifione, C0 < CH = CH > C0 - (P- 2 °9)- 

Acetanilide (phenyl acetamide, antifebrine) , 

//° 
CH3C \ NHC 6 H/ 

is prepared by boiling for some hours a mixture of aniline 
with one and a half times its weight of glacial acetic acid, 
in a flask connected with an upright condenser. It may 
be crystallized from hot water, alcohol, or benzene. It melts 
at 1 1 6°, and boils at 304 . It is used in medicine. 
Acetanilide may be considered as phenyl acetamide, 

//° 
CH 3 CH \ NHC G H 5 ' 

as the acetyl derivative of aniline, C H 5 NH(C 2 H 3 O), or as the 
anilide of acetic acid, CH 3 CO ■ NHC 6 H 5 . The three designa- 
tions all refer to an identical structure, of course, but illus- 
trate the fact that it is often practically convenient to use 
different names for the same compound. In the present case, 
one name or the other would be more convenient according 
to whether a study was being made of the amide, the amine, 
or the acid. 

Aniline and its homologues are not very stable toward 



METHYL ANILINE. 44 1 

many reagents, but the acetyl derivatives are much more 
stable. In many cases, therefore, the aromatic amines may be 
converted into acetyl derivatives, and the latter may be oxi- 
dized, nitrated, or converted into halogen substitution pro- 
ducts, to much better * advantage than the original amine. 
The acetyl derivative of the substitution product may then 
be saponified by boiling with alcoholic potash or with an 
acid. 

Methyl Aniline (phenyl methyl amine), 

ch h ;> nh - 

When the sodium salt of acetanilide, C 6 H 5 NNa — COCH 3 , is 
treated with methyl iodide, methyl acetanilide, 

^>N-C : H s O, 

is formed. This gives, on saponification, methyl aniline, 
which boils at 193. 5 . Methyl aniline gives a nitroso 

compound, CeH5 >NNO, 

CH 3 

which readily rearranges itself to p-nitroso methyl aniline, 

NHCH 3 1 

Lfi 4< NO 4' 

When methyl aniline hydrochloride, C 6 H 5 NHCH 3 ■ HC1, 
is heated in a sealed tube to 300 , the methyl group wan- 
ders from the nitrogen to the nucleus, forming p-toluidine, 

QH4< CH 3 - 

The reaction is general in character, methyl or ethyl groups 
being transferred to the para position, if that is vacant, 
otherwise to the ortho position ; but meta compounds are 
never formed. This is known as Hofmann's synthesis of 



442 ORGANIC CHEMISTRY. 

aromatic amines, and is of great technical importance, as 
well as of scientific interest. 

Dimethyl Aniline, C 6 H 5 N(CH 3 ) 2 , is prepared by treating 
aniline with methyl iodide, or by heating aniline hydrochlo- 
ride with methyl alcohol to 280 . It boils at 194 , and has 

a specific gravity of 0.9575 at — 5 - 

4 

The para hydrogen atom of the benzene nucleus of 
dimethyl aniline is very easily attacked by a great variety 
of agents. Many such reactions give dyestuffs, or sub- 
stances which may be used in the preparation of dyestuffs, 
and are technically important. Thus, when dimethyl aniline 
is treated with chloranil, C 6 C1 4 2 , which acts as an oxidizing 
agent, methyl violet is formed. This is a mixture of 

/ C 6 H 4 N(CH 3 ) 2 / C 6 H 4 N(CH 3 ) 2 

C-C 6 H 4 N(CH 3 ) 2 and C - C 6 H 4 N(CH 3 ) 2 
I \C C H 4 NCH 3 HC1 I \ C 6 H 4 N(CH 3 ) 2 C1. 

The close relationship between this body and rosaniline, 

(NH 2 C 6 H 4 ) 2 C(OH)C 6 H 3 <^ K 

is worthy of notice. The latter is prepared by oxidizing a 
mixture of aniline and o- and p-toluidine with arsenic acid. 

Fuchsine, C 20 H 19 N 3 • HC1, the hydrochloride of rosaniline, 
may have a structure like that given for methyl violet, or 
each may have a quinoid structure (p. 264). 

The Toluidines, CH 3 C 6 H 4 NH 2 , 

and Xylidines, (CH 3 ) 2 C 6 H 3 NH 2 , 

resemble aniline in general properties, and require no especial 
consideration here. 



C 6 H 4 < 



PHENYLENE DIAMINE. 443 

Benzyl Amine, C 6 H 5 CH 2 NH 2 , is prepared by treating 
benzyl chloride, C 6 H 5 CH 2 C1, with ammonia, or by treating 
phenyl acetamide, C 6 H 5 CH 2 CONH 2 , with potassium hypo- 
bromite. It boils at 185 , and has a specific gravity of 

O o 

0.9826 at — '^- • It*is a strong base, and resembles the 
4 

aliphatic amines in its general properties. 
o-Phenylene Diamine, 

r it <r NU * x 

te±1 ^NH 2 2 

is prepared by the reduction of orthonitra7iiline, 

NH 2 1 

N0 2 2 

with tin and hydrochloric acid. It melts at 103 , and boils 
at 2 56°-2 58°. 

a-Methy lbenzimidazole , 

is an anhydride of the acetyl derivative of o-phenylenedia- 
mine, formed by boiling it with glacial acetic acid. It melts 
at 1 7 5 , and boils without decomposition. It is a strong 
base. Similar compounds are formed by other aromatic 
orthodiamines. 

m-Phenylene Diamine, 

rH NH : 1 
L,Hi< NH, 3' 

is prepared by the reduction of m-dinitrobenzene, 

C6H4< N0 2 3 ' 
It melts at 63 , and boils at 282°-284°. 



444 ORGANIC CHEMISTRY. 

Both ortho- and meta-diamines are characterized by pecu- 
liar reactions with nitrous acid (p. 468). 

p-Phenylene Diamine, 

CsH<< nh 2 4' 

is prepared by the reduction of p-nitracetanilide, 

NHC.H.O 1 
^ 6 4< N0 2 4' 

with tin and hydrochloric acid, the acetyl group being 
removed by the action of the acid during the reduction. It 
melts at 140 , and boils at 267 . It is easily oxidized to 
quinone, 

CO<r CH = CH ^CO 

a reaction characteristic of para diamines. 
Benzidine (4, 4 / -Diamino diphenyl), 



NH 2 , 



is formed by the rearrangement of hydrazo-benzene, 



-NH-NH- 



under the action of dilute acids, a reaction of very consider- 
able commercial importance (see p. 474)- 

a-Naphthylamine, 



NH 2 



(See p. 469). 



AC- TE TRAH YDRO-a-NAPH TH Y LA MINE. 44 5 

is prepared by the reduction of a-nitronaphthalene. It melts 
at 50 , and boils at 300 . It " couples " easily with diazo- 
benzene sulphonic acid, and is used for the detection of 
nitrites in water analysis. The compound formed is p-sul- 
phobe?izene-azo-a-naphthylamine, 

NH 2 SO3H 

CO o 

I— N = N — I 

Ar*-tetrahy dro-a-naphthy lamine , 

NH 2 

I 
CH 2 -CH. 7 -C-C CH 

I II • 

CH 2 -CH 2 -C-CH = CH 

is formed by the reduction of a-naphthylamine by means of 
amyl alcohol and sodium. It boils at 277 , and has a specific 
gravity of 1.0625 at I6 3 . It has the characteristics of an 
aromatic amine, being a very weak base, and " coupling " 
easily with diazo compounds. (See above.) Potassium per- 
manganate oxidizes it to adipic, 

CRL-CH CO,H 

I 
CH 2 -CH 2 C0 2 H 

and oxalic acids. 

Ac-tetrahy dro-a-naphthy lamine , 

NH 2 

I 
CH = CH-C-CH -CH 2 

I II I , 

CH = CH-C-CH 2 -CH 2 

* The prefixes " ar- " and " ac- " are abbreviations of aromatic and alicyclic, and 
indicate whether the amino group is connected with the aromatic or alicylic nucleus. 



446 



ORGANIC CHEMISTRY. 



is formed by reducing 1.5 diaminonaphthylene, and eliminating 
the amino group from the aromatic nucleus. It boils at 
246. 5 . It has the characteristics of an alicyclic amine (p. 
424), is a strong base, gives no diazo derivative, does not 
" couple " with diazo compounds, and gives a stable nitrite. 
It is oxidized to phthalic acid by potassium permanganate. 

Quinoline, 

CH CH 

// \ / % 

CH C CH 

I II I , 

CH C CH 

^ / \ // 

CH N 

is found in coal-tar, and is formed by the distillation of qui- 
nine, cinchonine, or strychnine with potassium hydroxide. 
It has been prepared synthetically by a number of methods, 
the most important being Skraup's synthesis, which consists 
in heating a mixture of aniline, glycerol, sulphuric acid, and 
nitrobenzene. The nitrobenzene acts chiefly as an oxidizing 



C 6 H 5 -NH 2 + C 3 H 8 3 + O = C 9 H 7 N + 4 H 2 

Aniline. Glycerol. Quinoline. 



Quinoline melts at — 19.5 , and boils at 238 . 
oxidized with difficulty, but then forms quinolinic acid, 



It is 




CO,H 



CQ 2 H 



a- METHYL HYDROXYLAMINE. 447 

This loses carbon dioxide when heated, and yields nicotinic 
acid, 



C0 9 H 



N 

The latter gives pyridine, of course, when heated with soda 
lime. 

Derivatives of Hydroxylamine. 

Closely related to the amines are the derivatives of hy- 
droxylamine. These are of two classes, a-alkylhydroxyl- 
amines, in which the hydrogen of the hydroxyl is replaced 
by the alkyl group ; and /3-alkylhydroxylamines, in which the 
hydrogen of the amino group is replaced. 

a-Methyl Hydroxylamine, NH 2 OCH 3 . — When benzaldox- 
ime and methyl iodide are added to a solution of sodium 
ethylate, and the mixture is heated for some time, methyl ben- 
zaldoxime is formed. This is decomposed by heating with 
concentrated hydrochloric acid, giving benzaldoxime and 
a-methyl hydroxylaminechloride : 

C 6 H 5 CH = NOH + C 2 H 5 ONa 

= C 6 H 5 CH-NONa + C 2 H 5 OH 
C 6 H 5 CH = NONa + CH 3 I = C 6 H 5 CH = NOCH 3 +NaI 

Methyl ester of 
benzaldoxime. 

C 6 H 5 CH = NOCH 3 + HC1 + H 2 

= C 6 H 5 CHO + NH 2 OCHgElCL 

The chloride of a-methylhydroxylamine melts at 149 . The 
chlorplatinate crystallizes in orange-red prisms or plates. 



44 8 ORGANIC CHEMISTRY. 

/3-Ethyl Hydroxylamine, C 2 H 5 NHOH. a.-Be?izylhydroxy la- 
mine, NH 2 OCH 2 C 6 H 5 , may be prepared by the methods just 
given, starting with acetoxime, 

JJj>C = NOH. 

When heated with ethyl bromide, this gives $-ethyl-o.-benzyl- 

Jiydroxylami7ie : 

NH 2 OCH 2 C 6 H 5 + C 2 H 5 Br = C 2 H 5 NHOCH 2 C 6 H 5 HBr. 

The last compound, when heated with concentrated hydro- 
chloric acid, gives /3-ethylhydroxylamine and benzyl chloride : 

C 2 H 5 NHOCH 2 C 6 H 5 + HC1 = C 2 H 5 NHOH + C 6 H 5 CH 2 Cl. 

The a- and /^-derivatives of hydroxylamine show the dif- 
ferences characteristic, in general, of compounds having alkyl 
groups combined with oxygen, or combined with carbon, 
nitrogen, sulphur, or other elements. In the former case the 
alkyl can usually be readily removed as a halogen alkyl 
compound ; in the other cases it cannot. This is illustrated 
in the last reaction given. 

Glycocoll (glycine, aminoacetic * acid), 

CH - C ° 2H 
CHsV NH 2 ' 

is formed by boiling gelatine with barium hydroxide or with 
dilute sulphuric acid, and by boiling hippuric acid with 
sulphuric acid. It is prepared by treating chloracetic acid, 
CH 2 C1C0 2 H, with ammonia. It is soluble in 4.3 parts of 
of cold water, but is insoluble in absolute alcohol. It melts 
witji decomposition at 2 7 ) 2°-2 2 > 6°. It has a sweet taste, and 
is neutral in reaction. Its chemical properties are indicated 

* Sometimes called amidoacetic acid. For the nomenclature used in this book 
see p. 289. 



HIPP URIC ACID. 449 

by its structure. It forms salts with both acids and bases, 
the salts with acids being acid in reaction, those with bases, 
alkaline. When treated with nitrous acid, it gives glycolic 
acid, rj r , C0 2 H 

CH2< OH * 
Sarcosine (methylglycocoll), 

C0 2 H 

L 2< nhch; 

is formed by boiling creatine or caffeine (p. 298) with barium 
hydroxide, or by treating chloracetic acid with methyl amine. 
It melts at 2io°-2i5°. 

Trimethylglycocoll (betain), 

^ 2< C0 2 H 

is found in cotton seed, in beets, and in a variety of 
vegetable and animal substances. It is the source of the 
dimethyl and trimethylamine obtained commercially by the 
destructive distillation of beet-sugar residues. When heated 
to ioo°, betain loses one molecule of water, and forms the 
cyclic ammonium salt, 

CO -O 

I I 

CH 2 -N (CH 3 ) 3 . 

Hippuric Acid (benzoylglycocoll) 



CH 2 < 



NHCOC 6 H 5 
^C0 2 H 



is found in the urine of cattle, horses (whence the name), 
and other herbivorous animals. If benzoic acid is taken 
internally, it is secreted in the urine as hippuric acid. It 
may be prepared by shaking a solution of glycocoll, 

C0 2 H 
CH '<NH 2 ' 



450 ORGANIC CHEMISTRY. 

and sodium hydroxide, with benzoyl chloride, C 6 H 5 C0C1. 
Hippuric acid melts at 187.5 °. It is difficultly soluble in 
cold water, alcohol, and ether. It is decomposed by boiling 
with mineral acids, or with alkalies, giving glycocoll and 
benzoic acid. 

Alanine (a-aminopropionic acid), is formed by the action of 
ammonia upon a-chlorpropionic acid. Of greater interest is 
its preparation by boiling a solution containing aldehyde am- 
monia, hydrocyanic acid, and hydrochloric acid. The reac- 
tion is general. 

r\rr CTSJ 

CH 3 CH< NH +HCN-^CH 3 CH< NH +HC1 

2 CO.H 

-*CH 3 -CH< , 



Leucine (a-aminocaproic acid), 

C0 2 H 



CH 3 CH 2 CH 2 CH 2 CH <^ 



is found in the spleen, pancreas, lymphatic and salivary 
glands, in the brain, in eggs, and extensively in the animal 
organism. In some diseases it is found in large amount in 
the liver. It can be prepared from horn, and has also been 
made synthetically. The leucine from natural sources is 
dextrorotatory. 

a-Asparagine (a-aminosuccinamidic acid) , 

CHNH 2 -CONH 2 

I 
CH 2 -C0 2 H 

is found in asparagus and in a great variety of plants. It 
exists in the right, left, and inactive forms, the laevorotatory 
form being most common in nature. Asparagine gives 
aspartic acid, 



AMINO-*-TOLUIC ACID. 45 I 

CHNH,C0 2 H 

I 
CH 2 C0 2 H 

on boiling with acids or bases. 

Anthranilic Acid (o-aminobenzoic acid) is formed when in- 
digo is boiled with a solution of potassium hydroxide. It is 
best prepared by treating phthalamidic acid, 

^ TT CONH 2 ,,>,.., ^ TT CO ATTT 

C 6 H 4 < , or phthahmide, C 6 H 4 < >NH, 

with sodium hypobromite (p. 422). Anthranilic acid melts 
at 1 44 - 1 45°. Its solution shows a blue fluorescence, and 
tastes sweet. It decomposes into carbon dioxide and aniline, 
on distillation. 

Anthranilic acid has recently acquired a very considerable 
technical interest from its use in the commercial synthesis of 
indigo. The proposal for its use depends partly on the fact 
that naphthalene, which is the commercial starting point in 
the synthesis, is cheap, and available in very large quanti- 
ties. 

o-Amino-a-Toluic Acid (o-amino phenyl acetic acid) , 

CH 2 C0 2 H 

Le 4< NH 2 

is only known in the form of its salts. When liberated 
from these it immediately decomposes into water and the 
anhydride, 

C 6 H 4 <^>CO, 

which is called oxindol. Oxindol possesses especial interest 
because of its relation to indigo. When indigo is oxidized 
with nitric acid, it gives isatine ; and this gives, by reduction, 
dioxindol, and by further reduction oxindol, and the last, by 



452 ORGANIC CHEMISTRY. 

distilling with zinc dust yields indol. The relations are as 
follows : 

C 6 H 4 <^>C = C<^>C 6 H 1 ->C c H 4 <^>CO 

Indigo. Isatine. 

->C 6 H 4 < CH ^ H )>CO^C 6 H 4 <^|>CO 

Dioxindol. Oxindoh 

Indol. 

Isatine was discovered very early in the study of indigo 
and its derivatives. For some years after that study was 
begun, the molecular weight of indigo was not known, and 
isatine seemed, at first, very closely related to indigo. This 
is clear if we use the empirical formula, and that corre- 
sponding to one-half the molecular weight of indigo, 

C 8 H 5 NO-*C 8 H 6 N0 2 . 

Indigo. Isatine. 

It appeared, from this relation, that it should be easy to 
pass back from isatine to indigo by reduction. The work 
which was done by Baeyer with this thought in mind led to 
the series of compounds given above. While this work did 
not lead to indigo, as had been hoped, it brought the discov- 
ery of the use of distillation with zinc dust as a powerful 
means of reduction. This method led, shortly after, to the 
reduction of alizarin to anthracene by Graebe and Lieber- 
mann, and then to the commercial manufacture of alizarin. 
(Baeyer, Ber. d. chem. Ges. 33, LII.) 

o-Amino Hydrocinnamic Acid, 

CELCH C(XH 



C 6 H 4 < N 



CARBOSTYRIL. 453 

is also unknown in the free state, as it passes spontaneously 
into the anhydride, hydrocarbostyril, 

CH CH 2 

// \ / \ 

CH C CH 2 . 

• I II I 

CH C CO 

^ / \ / 

CH NH 

This is formed by the reduction of o-nitrohydrocinnamic 
acid with tin and hydrochloric acid. 

Carbostyril (py-2-hydroxyquinoline) ,* 

CH = CH 
C 6 H 4 < | 

N=C-OH 

is the " enol " form of the anhydride of o-aminocinnamic acid, 



C 6 H 4 < 



CH = CH-C(XH 



NH 2 



The free acid may be obtained, in this case, by adding 
ferrous sulphate to a hot ammoniacal solution of o-nitrocin- 
namic acid. It melts at i58°-i 59°, and its solutions show a 
bluish green fluorescence. 

When, however, o-nitrocinnamic acid is reduced by warm- 
ing it with ammonium sulphide, carbostyril is formed. This 
crystallizes from alcohol in large prisms, which melt at 199 - 
200 . It is a weak base, and also a weak acid, partaking of 
the character of a phenol, and forming salts which are not 
decomposed by water, but which are decomposed by car- 

* The prefixes "py " and " bz " are abbreviations of pyridine and benzene, used to 
designate whether a derivative of quinoline has the substituent in the benzene or in the 
pyridine nucleus. 



454 ORGANIC CHEMISTRY. 

bonic acid. Treatment with phosphorus pentachloride con- 
verts carbostyril into py-2-chlorquinoli}ie, 

C 6 H 4 | 

, C CI 
\ N * 

and this can be reduced to quinoline by heating it to 240 
with glacial acetic and hydriodic acids. 
The ketone form of carbostyril, 

CH = CH 

C 6 H 4 I , 

x NH-CO 

is not known in the free state ; but, as often happens, alkyl 
derivatives of both ketone and enol forms have been pre- 
pared. Such alkyl derivatives are stable, while the mother 
substance may pass readily from one to the other of the 
" tautomeric " forms. The ethyl ester of carbostyril, 

CH-CH 
C 6 H 4 I , 

x N==C-OC 2 H 5 

is formed by warming py-2-chlorquinoline (see above) with 
alcoholic potash, from the silver salt of carbostyril and ethyl 
iodide, and, together with ethyl psendocarbostyril, by boiling 
an alcoholic solution of carbostyril with potassium hydroxide, 
and ethyl iodide. It boils at 2 66°, and is a strong base. It 
resembles the phenol ethers in being very stable toward 
alkalies, but it is decomposed into carbostyril and ethyl 
chloride by heating with hydrochloric acid to 120 . 



LABORATORY EXERCISES. 455 

Ethyl Pseudocarbostyril * (n-ethyl-a-quinolon), 
/CH=CH 
C 6 H 4 I , 

X N CO 

C 2 H 5 
is formed, in part, by boiling an alcoholic solution of car- 
bostyril with potassium hydroxide and ethyl iodide (see 
above), or by oxidizing quinoline iodoethylate, 

7 CH=CH 

X N=CH' 

/ \ 
I QH 5 

with an alkaline solution of potassium ferricyanide. It may 
be considered as the anhydride of ethylaminocinnamic acid, 

CH = CHC(XH 

Ce 4< NHC 2 H 5 

but has not, apparently, been prepared from that compound. 
Ethyl pseudocarbostyril is not decomposed by heating with 
hydrochloric acid to 150 (p. 448). It melts at 53°-55°, and 
boils at 3 i6 -3i8°. 

Laboratory Exercises. 

Preparation of the following substances : 



I. 


Diethylamine. 


8. 


p-Diaminobenzene 


2. 


Isopropyl amine. 


9- 


Benzidine. 


3- 


2, 4, 6-Trimethyl-pyridine. 


10. 


a-Naphthylamine. 




(7-collidine). 


11. 


Quinoline. 


4- 


Aniline. 


12. 


Glycocoll. 


5. 


m-Toluidine. 


13. 


Anthranilic acid. 


6. 


Acetanilide. 


14. 


Isatine. 


7- 


m-Diaminobenzene. 







* The prefix " pseudo " has been proposed by Baeyer to designate substances 
derived from a form of a compound which does not exist in the free state. As it is 
sometimes difficult to determine in which of the two tautomeric forms the free substance 
exists, other designations similar to the second given above are usually to be preferred. 



45 6 ORGANIC CHEMISTRY. 



CHAPTER XXI. 

DIAZO, AZO, HYDRAZO, AND OTHER NITROGEN 
COMPOUNDS. 

When a cold acid solution of an aromatic amine is treated 
with nitrous acid, ethyl nitrite, or amylnitrite, a salt of a 
diazo compound (a " diazonium " salt) is formed, 

C 6 H 5 NH 2 HC1 + HN0 2 = C 6 H 5 N 2 C1 + 2 H 2 0. 

Aniline hydrochloride. Benzene diazonium 

chloride. 

Structure of Diazo Compounds. — Early in the study of 
the diazonium salts, two formulae were proposed for them. 
Kekule supposed benzene diazonium chloride to be 

C 6 H 5 N = NC1, 

while Blomstrand, Strecker, and Erlenmeyer proposed the 

formula, C 6 H 5 N = N 

I 
CI 

which represents them as quaternary ammonium compounds. 
These formulae have been the occasion of prolonged discus- 
sion. Kekule's formula was thought to explain, more satis- 
factorily, the " coupling " reactions by which azo compounds 
are formed. Thus benzene diazonium chloride reacts with 
many amines and phenols, with elimination of hydrochloric 
acid, giving azo compounds, 
C 6 H 5 N 2 C1 + C 6 H 5 N(CH 3 ) 2 = C 6 H 5 N = NC 6 H 4 N(CH 8 ) 2 + HC1. 

Dimethyl aminoazobenzene. 

That the two groups are combined with different nitrogen 



NITROGEN COMPOUNDS. 457 

atoms in the azo compound is proved by the fact that it 
gives aniline and p-amino dimethylaniline, 

N(CH 3 ) 2 
CeH5< NH 1! ' 

by reduction. Blom'strand's formula, on the other hand, is 
more in accord with the method of formation of the diazo 
compounds : 

/H O ' 
C 6 H 5 N < H ^ N -»C 6 H 5 N = N. 

|\HH0 7 i 

CI I ! CI 

Blomstrand's formula also explains the " coupling " re- 
actions, if we assume an addition at first, giving the com- 
pound, 

C 6 H 5 N = N-C 6 H 4 N(CH 3 ) 2 . 
/ \ 
CI H . 

As the azo compounds are not basic, such a substance 
would at once split off hydrochloric acid and give the same 
final result as before. 

With alkalies, the diazo compounds also form salts, of 
which diazobenzene potassium, C 6 H 5 N 2 OK, is an illustration. 
When a strongly alkaline solution of diazobenzene potassium 
is heated, it is changed to is o diazobenzene potassium. Three 
formulae are possible for these salts, 

C 6 H 5 -NeeeN 

| ' C 6 H 5 N = N-0-K, 
OK 

C 6 H 5 N-N = 

I 
K 



458 ORGANIC CHEMISTRY. 

The second formula may also be given the stereomeric 
forms, 

C 6 H 5 -N C 6 H 5 -N 
II and || 

K-O-N N-O-K 

Syn-diazobenzene potassium. Anti-diazobenzene potassium. 

As with the formulae for the chloride, the difficulty of de- 
termining whether a given reaction takes place by addition 
or by substitution, has made the choice among these formulae 
nearly impossible. A detailed discussion of the questions 
involved cannot be given here. 

Fortunately, the practical use of the diazo compounds is 
scarcely affected by the question of their constitution. That 
practical use is very important, both in the laboratory and 
in technical manufacture. 

The diazo compounds are very unstable, and also very 
reactive. The salts with acids are often explosive, either by 
percussion or on heating. In general, the presence of nega- 
tive groups in the aromatic compound increases their 
stability, while the presence of positive groups decreases it. 
Thus the xylene diazonium chloride, 



C«H 



//(CH 3 ) 2 
\N 2 C1 ' 



is less stable, while p-nitro-benzene diazonium chloride, 
fH N.C1 



NO 



is more stable than benzene diazonium chloride, C 6 H 5 N 2 C1. 

The reactions of the diazo compounds are of two types : 
those in which the nitrogen is eliminated, and the group is 
replaced by some atom or group, and those in which the 
nitrogen atoms are retained, a stable hydrazine, azo com- 
pound, or hydrazone, being formed by reduction or " coup- 
ling." 



REPLACEMENT BY HYDROGEN. 459 

Replacement of the Diazo Group. 
Because of their instability, diazo compounds are very rarely 
separated, even in the form of their salts, but are usually 
prepared at a low temperature (often at o°) and employed 
for some further reaction with as little delay as possible. 
The replacement reactions are to be looked upon as a means 
of replacing the amino group of aromatic compounds by 
other atoms or groups. The most important replacement 
reactions are : 

i. Replacement by Hydrogen This is usually effected by 

boiling the diazo salt with alcohol : 

(C 6 H 5 N 2 ) 2 S0 4 + 2 C 2 H 5 OH = 2 C 6 H 6 + 2 N 2 + 2 C 2 H 4 + H 2 S0 4 . 

Benzene diazonium Benzene. Aldehyde, 

sulphate. 

Usually a cold solution of the amine in absolute alcohol, 
to which an excess of sulphuric acid has been added, 
is treated with the mixture of oxides of nitrogen evolved 
by warming arsenious oxide with nitric acid, or, as is 
frequently better, with the calculated amount of ethyl nitrite, 
C 2 H 5 — N0 2 . When the diazo compound has been formed, 
the solution is heated to boiling, and the reaction given 
above takes place. The reaction is to be considered as a 
reduction, the alcohol being oxidized. In a few cases other 
reducing agents have been used, but none of the other 
methods have acquired considerable importance. 

In some instances a second reaction occurs : 

(C 6 H 5 N 2 ) 2 S0 4 + 2 C 2 H 5 OH = 2C 6 H 5 OC 2 H 5 +N 2 +H 2 S0 4 . 

Ethyl phenyl ether 
(phenetol). 

Whether the diazo group shall be replaced by hydrogen 
or by the ethoxy (— O — C 2 H 5 ) group, depends partly on 
the nature of the compound, partly on the conditions of the 



460 ORGANIC CHEMISTRY. 

reaction, as to temperature and pressure, and partly on the 
nature of the alcohol used. (Remsen, A??i. Chem.J. 8, 243; 
9, 3%7 ; "> 3*9 '■> *5» io 5-) 

2. Replacement by Hydroxyl. — This occurs when the 
diazo compound is formed by adding sodium nitrite, care- 
fully, to a cold, aqueous, acid solution of the amine, and the 
solution is subsequently boiled, 

(C 6 H 5 N 2 ) 2 S0 4 +2H 2 = 2 C 6 H 5 OH+N 2 + H 2 S0 4 . 

Phenol. 

For a clean reaction it is usually important, not only that 
all of the amine should be converted into the diazo com- 
pound, but also that no excess of nitrous acid should be 
present. This may sometimes be secured by using a slight 
excess of the sodium nitrite and then adding some urea, 
which will decompose the excess of nitrous acid when the 
solution is boiled. 

3. Replacement by Halogens. — When a strongly acid solu- 
tion of a diazonium salt is added to a concentrated solution 
of potassium iodide, and the solution warmed, a nearly quan- 
titative replacement of the diazo group by iodine can usu- 
ally be secured : 

C 6 H 5 N 2 I = C 6 H 5 I + N 2 . 

Benzene diazo- lodo- 
nium iodide. benzene. 

Similar reactions may occur, to a limited extent, with 
hydrochloric or hydrobromic acid ; but the yields are so 
small as to make the method practically worthless. The 
yields may be increased so far as to be satisfactory by a 
variety of methods, the one having greatest practical signifi- 
cance being known as " Sandmeyer's reaction." This con- 
sists in pouring the solution of a diazonium salt into a 
warm solution of cuprous chloride or cuprous bromide. The 
most advantageous temperature varies in different cases. 



REPLACEMENT BY CYANOGEN. 46 1 

C 6 H 5 N 2 C1 + Cu 2 Cl 2 = C 6 H 5 N 2 Cl,Cu 2 Cl 2 = C 6 H 5 C1 + N 2 + Cu 2 Cl 2 

Chlorbenzene. 

(Sandmeyer, Ber. d. chem. Ges. 17, 1633, 2650 (1884); 23, 
1880 ; Erdmann, Am. Chem. (Liebig) 272, 141, (1893).) 

Beside the formation of tarry matters, which always occurs 
to a greater or les£ extent in connection with diazo re- 
actions, two other reactions may occur which reduce the 
yield : 

C 6 H 5 N 2 C1 2 + H 2 = C G H 5 0H + N 2 + 2 HC1 ; 

2C 6 H 5 N 2 Cl + Cu 2 Cl 2 = C 6 H 5 N = NC 6 H 5 + 2 CuCl 2 . 

Azobenzene. 

The first is the usual decomposition of diazonium salts 
with water, and takes place when the solutions are not prop- 
erly mixed, while the second seems to be favored by too 
slow a decomposition of the double compound which is 
formed when the solutions are mixed. 

The diazo group may be replaced ' by fluorine by adding 
piperidine to a solution of a diazonium salt, and decom- 
posing the resulting diazo piperidide (see diazo amino com- 
pounds p. 464), with concentrated hydrofluoric acid, 

C 6 H 5 N 2 Cl + C 5 Hi = NH = C 6 H 5 N = N-N = C 5 H 10 -r-HCl 

Piperidine. Diazobenzene piperidide. 

C 6 H 5 N = N-N = C 5 H 10 +H 2 F 2 =C 6 H 5 F + N 2 + C 5 H n N.HF. 

Fluor- 
benzene. 

4. Replacement by Cyanogen is also effected by Sand- 
meyer's reaction, the cuprous chloride solution being replaced 
by one of cuprous cyanide, 

C 6 H 5 N 2 Cl + Cu 2 C 2 N 2 =C G H 5 N 2 Cl,Cu 2 C 2 N 2 (?) 
= C 6 H 5 CN + N 2 + Cu 3 <£ N (?). 

Benzonitrile ^1 

(phenyl cyanide). 

The nitrile formed can, of course, be saponified to an acid. 



462 ORGANIC CHEMISTRY. 

5. Replacement by Hydrocarbon Residues takes place in 
some cases when diazonium chlorides are heated with aro- 
matic hydrocarbons, pyridine, quinoline, thiophene or similar 
compounds, with or without the presence of aluminium 
chloride. 

C 6 H 5 N 2 C1+C 6 H 6 =C 6 H 5 -C 6 H 5 +N 2 + HC1. 

Diphenyl. 

6. Replacement by Sulphur, the Sulphonic, Nitro, and other 
Groups has been effected in isolated cases, but usually with 
extremely poor yields, and the methods are of no practical 
importance. 

The second class of reactions for the diazo compounds, 
in which hydrazines, hydrazones, diazoamino, aminoazo 
and hydroxy azo (" oxyazo ") compounds and diazoimides are 
formed,' will be considered under the head of these various 
classes of compounds. 

Comparatively few aliphatic diazo compounds are known, 
and these appear to have a somewhat different structure 
from the aromatic ones. The most important of them is, 

Diazo-acetic Ester, 

N 

|| >CH-C0 2 C 2 H 5 . 

N 

This is formed when the hydrochloride of glycocoll ester is 
treated with sodium nitrite. 

C0 2 C 2 H 5 

CH 2<NHHCl + NaN ° 2:=CH ~ N +NaCl + 2H 2 0. 

2 \ II 

\N 

Diazo-acetic ester is a yellow oil which melts at — 22 , 
and boils at 84° under a pressure of 6i° mm. It is unstable 



TR1AZO ACETIC ACID. 463 

and liable to explode, especially if impure. It is very re- 
active, resembling the aromatic diazo compounds in a gen- 
eral way, but it also exhibits some noteworthy differences. 
It has been used in some important syntheses, and this use 
seems likely to be extended. 

Diazoacetic Acid, N 

|| >CH-C0 2 H, 

N 

can, apparently, exist only in solutions of its salts, and is 
even then very unstable. 

Triazoacetic Acid, CH— C0 2 H 

II II 

N N 

I I 

C0 2 H-CH-N = N-CH-C0 2 H, 

is obtained in the form of its sodium salt when diazoacetic 
ester is introduced, slowly, into a very concentrated, hot 
solution of sodium hydroxide. The free acid crystallizes in 
yellow plates which, decompose at 149 . 

Triazoacetic acid is of especial interest because, by its 
decomposition with acids, hydrazine, H 2 N — NH 2 , was first 
prepared. 

N = N-CH-C0 2 H 

\ 
N 
CH-C0 2 H || +6HC1 + 6H 2 

N 
/ 
N = N-CH-C0 2 H 

NH 2 HC1 C0 2 H 

=3 1 +3 1 

NH 2 HC1 C0 2 H 

Hydrazine hydrochloride. 



464 ORGANIC CHEMISTRY. 

Diazoamino Compounds* 

If a diazo salt is brought together with an amine in a 
neutral or faintly acid (acetic acid) solution, a diazoamino 
compound is formed. The fact that the reaction takes place 
best in a nearly neutral solution indicates that it is the 
diazo hydroxide, formed by the hydrolysis of the diazo salt, 
which takes part in the reaction. 

QH 5 N 2 OH + C G H 5 NH 2 = C 6 H 5 N = N - NHC 6 H 5 + H 2 0. 

Diasobenzene Aniline. Diazoamino benzene, 

hydroxide. 

It would seem, from the method of formation, that with 
two different amines two isomeric compounds should be 
obtained, thus, 

C 6 H 5 N = N - NHC 6 H 4 Br and BrC 6 H 4 N = N - NHC 6 H 6 . 

It has been found, however, that, no matter which amine 
is converted into the diazo compound, the same final pro- 
duct results. This has led some to question the explanation 
of their formation which has been given. It would seem 
rather that the form at first produced passes at once into 
the other form, if that is more stable. This may happen 
thus : 
C 6 H 5 N = N - NHC 6 H 4 Br -» C 6 H 5 NH - N(OH)NHC 6 H 4 Br 
-*C C H 5 NH - N = N - C 6 H 4 Br. 

Another explanation is that the diazo hydroxide has the 
formula R — N = N — OH, in which case the compound R — 
NH-N(OH)-NH-R' may always be at first formed by 
addition of the amine to the diazo hydroxide. 

The diazoamino compounds are, perhaps, best considered 
as anilides of the diazo hydroxides, considering the latter as 

* These compounds are often called " diazoamido compounds." It seems better 
here and in the following pages to retain the distinction between "amino" and 
" amido " already made (p. 289). 



TRIAZOACETIC ACID. 46$ 

acids. In accordance with this view they may be saponified, 
in some cases, by careful treatment with acids, giving diazo- 
nium salts and amines. 

C 6 H 5 N = N - NHC 6 H 5 + 2 HBr = C 6 H 5 N 2 Br + C 6 H 5 NH 2 HBr. 

The diazoamino compounds are usually well crystallized, 
comparatively stable compounds. They retain, however, a 
close relationship to the diazo compounds, and most of their 
reactions are easily understood from that fact. Thus, further 
treatment with nitrous acid, in an acid solution, converts both 
parts into a diazo compound ; boiling with dilute acids gives, 
usually, a phenol and an amine : 

C 6 H 5 N = N-NHC 6 H 5 +HC1+H 2 

= C G H 5 OH + N 2 + C C H 5 NH 2 HC1. 

They also form hydroxy azo compounds (see these) with 
phenols : 

C 6 H 5 N = N-NHC 6 H 5 +C 6 H 5 -OH 

= C 6 H 5 N = N - C G H 4 OH + C C H 5 NH, 

p-Hydroxyazobenzene. 

The diazoamino compounds are very weak bases. They 
form, in some cases, unstable chlorplatinates, as 

(C 6 H 5 N 3 HC 6 H 5 ) 2 H 2 PtCl 6 . 

They also yield metallic compounds, as 

C 6 H 5 N 3 NaC 6 H 5 . 

These are usually decomposed by water, but the presence 
of nitro groups in the benzene nucleus may render them 
somewhat more stable. 

The most important reactions of the diazoamino com- 
pounds are those by which they are converted into a7iiinoazo 
bodies. ( See below.) 



466 ORGANIC CHEMISTRY. 

Diazoamino Benzene, C 6 H 5 N = N — NHC 6 H 5 , is prepared 
by adding one-half molecule of sodium nitrite to a solution 
containing one molecule of aniline hydrochloride, and then 
adding some sodium acetate, keeping the temperature at 
25 — 30 . It crystallizes from benzene in flat, yellow prisms 
which melt at 9 6°. 

Aminoazo Compounds * 
The aminoazo compounds may be prepared : 

1. By nitration and subsequent reduction of azo com- 
pounds : 

C 6 H 5 N = N-C 6 H 5 ->- C 6 H 5 N = N-C 6 H 4 N0 2 

Azobenzene. Nitroazobenzene. 

->- C 6 H 6 N = N-C C H 4 NH 2 

Aminoazobenzene. 

2. By the " coupling" of a diazo compound with an aro- 
matic amine : 

C 6 H 5 N 2 C1 + C 6 H 5 N(CH 3 ) 2 = C 6 H 5 N = N-C 6 H 4 N(CH 3 ) 2 

Benzene diazonium Dimethyl aniline. p-Dimethylaminoazobenzene. 

chloride 

The azo group enters in the para position with reference 
to the amino group, if that is free, otherwise in the ortho 
position. The structure of the resulting compounds can 
usually be determined by reduction, thus : 

C 6 H 5 N = NC 6 H 4 N(CH 3 ) 2 + 4 H 

= C 6 H 5 NH, + NH 2 - C 6 H 4 N(CH 3 ) 2 . 

p-Dimethyl phenylene diamine. 

That the reaction just given is susceptible of a very great 
variety of applications is evident. In the benzene series 

* Sometimes called " amidoazo " compounds. The name " azo " is applied to sub- 
stances containing the group — N=N — . (See p. 47 2 -) 



AMINOAZOBENZENE. 467 

dialkyl-amines and meta-diamines react with especial ease. 
Naphthylamine and its derivatives also react very easily. 
For the importance of the reaction in the preparation of 
dyes, see below under hydroxyazo compounds. 

3. By the rearrangement of diazoamino compounds: 
C ? H 5 N = N-NHC 6 H 5 = C 6 H 5 N = N-C 6 H 4 NH 2 . 

Diazoamino benzene. p-Aminoazo benzene. 

This is to be considered as merely a special application of 
the second case, a separation of the diazo group preceding 
the formation of the aminoazo body. 

The aminoazo compounds are weak bases. They form 

diazo compounds when their acid solutions are treated with 

nitrous acid, and in most respects conduct themselves as 

true amines. Some of their properties, however, indicate 

that they may also exist in a tautomeric quinoid form which 

may be designated as a hydrazone of a quinonimide, thus : 

pit cy\ 

C 6 H 5 NH-N = C< CH ~ CH >C = NH. 

The difference in color which often exists between the free 
compounds and their salts may possibly indicate a change 
from one form to the other. 

p-Aminoazobenzene, C 6 H 5 N = N — C 6 H 4 NH 2 , is formed by 
the reduction of p-nitroazobenzene. It is most easily pre- 
pared by warming diazoaminobenzene gently with aniline 
hydrochloride and aniline (see above). It crystallizes in 
yellow leaflets, which melt at i26°-i2 7°, and boil without 
decomposition at a temperature above 360 . The great 
stability, in comparison with the isomeric diazoamino com- 
pound, is noteworthy. It gives, by reduction, and in part by 
merely boiling with hydrochloric acid, aniline, and p-pheny- 
lene diamine. 



468 ORGANIC CHEMISTRY. 

The hydrochloride crystallizes in violet needles. 

p-Aminoazobenzene is known as " aniline yellow," and in 
slightly acid solution it colors silk or wool a deep yellow. Its 
salts are easily hydrolyzed by water. 

p-Dimethylaminoazobenzene, C 6 H 5 N = N — C 6 H 4 N(CH 3 ) 2 , 
prepared from benzene diazonium chloride and dimethyl- 
aniline (see above), crystallizes in yellow leaflets, which melt 
at 1 1 7 . The hydrochloride forms very fine purple-red 
needles. 

4-Sulpho-4'-dimethylaminoazobenzene. (Helianthin, Orange 
III, Tropablin D), 

N = N-C 6 H 4 N(CH 3 ) 2 i 
^ 6 4< S0 3 H 4 

is formed either from p-sulphocliazobenzene and dimethyl 
aniline, or from p-dimethylaminoazobenzene by treatment 
with fuming sulphuric acid. It crystallizes in small violet 
leaflets. The sodium salt, 

N = N-C 6 H 4 N(CH 3 ) 2 
^ 6H4< S0 3 Na 
is known as "methyl orange," and is much used as an indi- 
cator. This use depends on the fact that the negative ion of 
the acid, which is present in solutions of its salts, is pure yel- 
low in color, while the free acid is pink. The acid is suffi- 
ciently strong so that the salts are scarcely affected by 
carbonic acid, and the indicator is especially useful in pres- 
ence of carbonic acid and ammonia. For the same reason 
it is almost useless for the titration of organic acids. 

3,2',4'-Triaminoazobenzene, 

NH, 



NH 2 



HYDROXY AZO COMPOUNDS. 469 

is formed, together with other compounds, when a nitrite is 
added to a faintly acid solution of m-phenylene diamine. It 
melts at 143. 5 ; and it is easily soluble in alcohol and ether, 
insoluble in ligroin, and difficultly soluble in water. As the 
compound forms in a very dilute solution of a nitrite, and has 
a deep yellow color/ m-phenylene diamine is sometimes used 
in the qualitative or quantitative determination of nitrous 
acid. While one part of nitrogen, as a nitrite, in thirty mil- 
lion of water can be detected by it, the reaction is not suffi- 
ciently sensitive for the purposes of water analysis. 

p- Sulphobenzene- azo- a- naphthy lamine, 

SOoH NH, 



6 



-N = N— I 

is formed when a solution of p-sulphobenzene diazonium 
chloride is added to a solution of a-naphthylaminechloride. 

C « H < < N?U +C U H,NH 2 = C 6 H< < £f_c l0 H 6 NH 2 +HC1 - 

It crystallizes in microscopic needles of a dark violet 
color. It is almost insoluble in water, very difficultly soluble 
in alcohol. It forms a red crystalline sodium salt, C^H^Ng 
S0 3 Na, which is soluble in water, but almost insoluble in a 
solution of sodium hydroxide. 

As sulphobenzenazonaphthylamine is formed slowly, but 
almost quantitatively, when sulphanilic acid and naphthy 1- 
amine hydrochloride are added to dilute solutions containing 
nitrous acid, and as it imparts to the solutions an intense 
red color, the reaction is much used in water analysis. 

Hydroxyazo (or oxyazo) Compounds Diazo compounds 

" couple " with phenols even more easily than with amines. 



470 ORGANIC CHEMISTRY. 

C 6 H 5 N 2 OH + C 6 H 5 OH = C 6 H 5 N = N-C 6 H 4 OH 

Phenol. p-Hydroxyazobenzene. 

The azo group enters para to the hydroxyl, if that posi- 
tion is free, otherwise in the ortho position. If two mole- 
cules of the diazo salt are present for one of the phenol, 
hydroxydisazo compounds are formed. Thus phenol-2 ,4-dis- 
azobenzene. 



C fi H r -N 9 -/ >OH 



N 2 C 2 H 5 , 

may be prepared in this manner from benzene diazonium 
nitrate and phenol. 

The parahydroxyazo compounds conduct themselves in 
general as phenols. Since, however, p-hydroxyazobenzene 
may also be prepared from p-nitrosophenol (quinone mon- 
oxime, p. 210) and aniline, it seems probable that they may 
have, in some cases, and perhaps often, a quinoid structure. 



= NIOH H IHNC 6 H 5 



0=< \=N-NHC 6 H 5 . 



This makes the hydroxyazo compounds hydrazones of the 
quinones. The orthohydroxyazo compounds exhibit less of 
the phenol character than the para compounds, and conduct 
themselves as hydrazones of orthoquinones. 

p-Hydroxyazobenzene (oxyazobenzene) , 

C 6 H 5 N = N-C 6 H 4 OH, 



AZOXY COMPOUNDS. 47 1 

is formed by adding a solution of potassium or sodium ni- 
trite to a dilute solution containing equal parts of phenol 
and aniline nitrate. It crystallizes in orange-colored rhom- 
bic prisms, and melts at 152 . 

4-Sulpho-2 ', 4 / -dihy droxy azobenzene , 

N = NC 6 H 3 (OH) 2 
Ce 4< S0 3 H 

4 

is formed from p-sulphodiazobenzene and resorcinol. Its 
sodium salt is known as " Crysoin," or " Tropaolin O." 

Azoxy Compounds. 
The azoxy compounds, 

R-N-N-R, 

\ / 

O 

are isomeric with the hydroxyazo compounds, and much less 
important. They are formed by the reduction of nitro com- 
pounds by boiling with alcoholic potash, by treatment with 
sodium amalgam, or with a solution of stannous chloride in 
sodium hydroxide, 

2 C 6 H 5 N0 2 - 3 = C 6 H 5 -N-N-C 6 H 5 . 

O 

Azoxybenzene. 

Mild reducing agents convert the azoxy compounds into 
azo or hydrazo derivatives, more vigorous reduction converts 
them into amines. Concentrated sulphuric acid converts 
them into hydroxyazo compounds (see Lachman, /. Am. 
Chem. Soc. 24, 1178). 



472 ORGANIC CHEMISTRY. 

Azo Compounds. 

Bodies containing the group R — N = N — R are called azo 
compounds. The preparation of such substances by means 
of diazo compounds has just been considered. What may 
be regarded as the mother substances are prepared by the 
reduction of nitro compounds, usually by means of zinc dust 
and alcohol : 

2 C 6 H 5 N0 2 +8H = C 6 H 5 N = NC 6 H 5 + 4 H 2 0. 

Nitrobenzene. Azobenzene. 

In some cases it is practically easier to carry the reduction 
a step farther, causing the formation of hydrazo compounds, 
and to oxidize the latter to azo derivatives. 

Azo compounds may also be formed by the oxidation of 
amines, and by the action of nitroso compounds on amines : 

2C 6 H 5 NH 2 + 2 = C G H 5 N = NC 6 H 5 +2H 2 
C 6 H 5 NO + C c H 5 NH 2 = C H 5 N = NC 6 H 5 +H 2 O. 

Nitrosobenzene. 

Substances containing two azo groups are called " disazo " 
compounds, thus : 

N = NC C H 5 N = NC 6 H 5 

C ° H *<N = NC 6 H 5 (HO)2C « H2< N = NC H/ 

Benzenedisazobenzene. Resorcinoldisazobenzene. 

The azo group gives to substances containing it neither 
acid nor basic properties. There is no replaceable hydrogen 
connected with the nitrogen, or with an adjacent carbon 
atom ; and the nitrogen retains so slight an affinity for acids 
that compounds with the halogen acids can only be formed 
when water is excluded. 

Reduction converts azo compounds at first to hydrazo 
compounds and then to amines. 



HYDRAZO COMPOUNDS. 473 

C 6 H 5 N = NC 6 H 5 + 2 H = C 6 H 5 NH-NHC 6 H 5 

Hydrazobenzene. 

C 6 H 5 NH-NHC 6 H 5 + 2 H = 2.C 6 H 5 NH 2 . 

Comparatively few aliphatic azo compounds are known, 
and these require no especial mention. 

The azo compounds are always deeply colored. 

Azobenzene, C 6 H 5 N = NC 6 H 5 , is prepared by the reduction 
of nitrobenzene with zinc dust and sodium hydroxide in an 
alcoholic solution, or by the oxidation of hydrazobenzene by 
the air, or by nitrous acid. It crystallizes in orange yellow 
leaflets, which melt at 68°, and boil at 293 . Solutions of 
azobenzene have a deep orange color, but it is not a dye 
(see below). 

Hydrazo Compounds. 

Hydrazo compounds contain the group R-NH-NH-R, 
and are prepared by the reduction of nitro compounds or of 
azo compounds : 

2 C 6 H 5 N0 2 +ioH = C 6 H 5 NH-NHC 6 H 5 + 4 H 2 

Hydrazobenzene. 

C 6 H 5 N = NC 6 H 5 + 2 H = C 6 H 5 NH-NHC 6 H 5 . 

The hydrazo compounds are colorless. As many other 
colored bodies give colorless compounds by reduction, a 
general name, " leuco " (from Xevkos, white), has been pro- 
posed to designate such substances. The hydrazo com- 
pounds are the u leuco " compounds corresponding to the 
azo bodies. 

• The aromatic hydrazo compounds are not basic in their 
properties, but mixed hydrazo bodies having on one side an 
aliphatic or alicyclic residue, may be weak bases. 



474 ORGANIC CHEMISTRY. 

When heated with dilute acids the hydrazo bodies undergo 
a highly interesting and commercially very important change, 
known as the benzidine rearrangement : 

C 6 H 5 NH-NHC 6 H 5 = NH 2 C 6 H 4 - C 6 H 4 NH 2 . 

Benzidine 
(4,4 / -Diamino diphenyl.) 

In many cases the reduction and rearrangement of the 
azo compounds may be carried out simultaneously by the 
action of an acid, alcoholic solution of stannous chloride. 

If the para position is free, the phenyl groups unite 
chiefly in that position, and the reaction is to be considered 
as another illustration of the loosening effect exerted by 
the amino group upon a hydrogen atom in the para position 
(pp. 209 and 466). 

If the para position is occupied, the rearrangement may 
cause a condensation in the ortho position. Thus ben- 
zene hydrazodimethylaniline gives, by rearrangement, 2,5,4'- 
dimethyltriamino diphenyl : 



(CH 3 ) 2 N< \NH-NH 



NH 2 

NH 2 




N(CH,) S 



In some cases a rearrangement occurs which gives a deriv- 
ative of diphenylamine. This is, in some sense, a halfway 
rearrangement and gives " semidines." Thus p-toluene- 
hydrazodimethylaminobenzene gives, by rearrangement, an 
orthosemidine : 



HYDRAZO COMPOUNDS. 475 



(CH 3 ) 2 N < >— NH— HN— < >CH 



(CH 3 ) 2 N 



CH, 



-NH- 



NH 2 

(Boyd,/. Chem. Soc. (London), 65, 879). 

Whether the benzidine or semidine rearrangement shall 
take place in a given case depends on the nature of the 
groups present. 

As the benzidines are aromatic compounds having two 
primary amino groups, these may be converted, by nitrous 
acid, into diazo groups, and the resulting compounds " cou- 
pled " with amines or phenols.. This gives rise to disazo 
compounds of the general formula, 

X-N = N-C 6 H 4 -C 6 H 4 -N = N-Y. 

These disazo bodies derived from benzidine form the 
very important group of dyes known as the " congo " series. 
By varying the substances combined, it has been possible to 
secure dyes of almost every color. These dyes are " sub- 
stantive " in character (p. 481). 

In the study of these dyes the following interesting laws 
have been discovered. The dyes which are technically valu- 
able are obtained from derivatives of benzidine having sub- 
stituents in the ortho position to one or both amino groups, 
that is, of the types, 



NH 2 < >-\ ;ne 



476 ORGANIC CHEMISTRY. 



and nh 2 ( \ — / )nh 2 




R 

Benzidine derivatives with groups in the meta position 
have little value for the preparation of dyes unless such a 
group or groups form a secondary ring, thus : 

nh ^CX^O nh2 - 

Hydrazobenzene, C 6 H 5 NHNHC 6 H 5 , is prepared by boiling 
nitrobenzene with alcohol, sodium hydroxide, and zinc dust. 
It crystallizes in colorless plates, which melt at 13 1°. In an 
alcoholic solution it is rapidly oxidized to azobenzene by the 
oxygen of the air. Acids transform it into benzidine. 

HYDRAZINES. 

Hydrazines bear the same relation to hydrazine, NH 2 -NH 2 , 
as amines bear to ammonia. They are usually prepared by 
the reduction of nitroso or diazo compounds : 

(CH 3 ) 2 NNO + 4 H = (CH 3 ) 2 N - NH 2 + H 2 0. 

Nitrosodimethylamine. Dimethylhydrazine. 

NO N<r NHa 

CO< NH ! CHs++H = CO< NH ! CH8+HA 

Nitrosomethyl urea. Hydrazinemethyi urea. 

AT NH 9 

C0< NH 3 +3 HC1 + H 2 

NHCH3.HCI 
= I +C0 2 +NH 4 C1. 

NH 2 .HC1 

Methylhydrazine 
hydrochloride. 

C 6 H 5 N 2 C1 -f- 4H = C C H 5 NHNH 2 • HC1. 

Phenylhydrazine hydrochloride. 



PHENYLHYDRAZINE. 477 

Aromatic hydrazines are also prepared by treating diazo- 
nium salts with acid sodium sulphite, and decomposing with 
hydrochloric acid, the hydrazosulphonic acids which result. 

C 6 H 5 N 2 C1 + NaHS0 3 = C 6 H 6 N = N- S0 3 H + NaCl, 

» Benzene azosulphonic acid. 

C 6 H 5 N = N-S0 3 H-f- 2 H = C 6 H 5 NH-NHS0 3 H, 

Benzene hydrazosulphonic 
acid. 

C 6 H 5 NHNHS0 3 H + HC1 + H 2 

= C 6 H 5 NHNH 2 HC1+H 2 S0 4 . 

Phenylhydrazine hydrochloride. 

The aliphatic hydrazines are strong bases, forming two 
classes of salts, as 



NHCH 3 


•HC1 


and 


NHCH 3 HC1 

1 


NH 2 






NH 2 HC1 



The second molecule of acid is, however, held much less 
firmly than the first. 

The aromatic hydrazines form stable salts only with one 
molecule of a monobasic acid. 

The hydrazines reduce Fehling's solution. In the aro- 
matic series oxidation of hydrazines with cupric sulphate or 
ferric chloride is occasionally used for the elimination of the 
amino group, instead of the more usual diazo reaction (p. 
459). (Haller, Ber. d. chem. Ges. 18, 90, 92, 786.) 

Phenylhydrazine, C 6 H 5 NHNH 2 , is most easily prepared 
in small quantities by reducing beiizenediazonium chloride 
with stannous chloride (see above). When pure, phenylhy- 
drazine is a colorless oil, which solidifies at a low tempera- 
ture, and melts at 24.1 . It boils with slight decomposition 
at 2 43. 5 , and is best distilled under diminished pressure. 
It darkens on exposure to the air, and usually has a red- 



478 ORGANIC CHEMISTRY. 

dish brown color. It is oxidized by Fehling's solution with 
formation of aniline, benzene, and phenol. It is a violent 
poison. 

HYDRAZONES, OSAZONES. 

The formation of hydrazones from aldehydes and ketones 
(pp. 179 and 189) has already been mentioned; also the 
formation of osazones from sugars (p. 364). 

Compounds of the type of acetoacetic ester, malonic ester, 
and 1,3-diketones, containing the group, — CO-CH 2 — CO— , 
or the group, — CH 2 — N0 2 , couple with diazo compounds 
to form hydrazones. Thus malonic ester gives, with ben- 
zene diazonium chloride, the hydrazone of mesoxalic acid : 



C0 2 C 2 H 5 
C0 2 C 2 H 5 



C 6 H 5 N 2 C1 + CH 2 < 

^w 2 ^ 2 x 

= c 6 h 5 nhn = c < r;;?;?;? + hci. 



C0 9 C 2 H 5 
r " li= ^C0 2 C 2 H 6 ' 



The reaction is closely analogous to the formation of 
oximes, from compounds containing the group, — CO — 
CH 2 — , when treated with amyl nitrite (p. 201). 

DIAZOIMIDES. 

Diazoimides contain the group, 

/N 

-N ||, • 

\ N 

and are prepared by treating diazo perbromides with ammo- 
nia, hydrazines with nitrous acid, or diazonium salts with 
hydrazoic acid. 

/ N 
C 6 H 5 N 2 Br 3 4-NH 3 = C 6 H 5 -N || + 3 HBr. 

\ N 

Diazobenzene Diazobenzene imide. 

perbromide. 



DIAZOBENZENIMIDE. 479 

C 6 H 5 NHNH 2 + HN0 2 = C 6 H 5 N(NO)NH 2 + H 2 0. 

Nitrosophenylhydrazine. 

C 6 H 5 N(NO)NH 2 = C 6 H 5 -N || + H 2 0. 

\ N 

(C 6 H 5 N 2 ) 2 S0 4 + 2 N 3 H = C 6 H 5 N 3 + H 2 S0 4 + 2 N 2 . 

Hydrazoic Diazobenzene 
acid. imide. 

A diazomide having a nitro group in the ortho or para 
position can be decomposed by alkalies giving a nitrophenol 
and a salt of hydrazoic acid : 
N 
(N0 2 )C 6 H 4 N< || + 2 KOH = (N0 2 )C 6 H 4 OK+N 3 K+H 2 0. 

N 
This reaction, and the last reaction for the preparation 
of the diazoimides, illustrate the close resemblance between 
the chemical properties of hydrochloric and hydrazoic acids. 

Diazobenzenimide (Triazobenzene, phenyl cyclotriazene) , 

N 
C 6 H 5 N< || , 

N 

is prepared by treating a solution of benzene diazonium 
chloride with one-half a molecule of stannous chloride. It 
is a light yellow oil, which boils at 73.5 under a pressure of 
22-24 mm., and has a specific gravity of 1.0853 at 2 5°* It 
explodes when distilled under ordinary pressure. 

Dyes. 

A dye is a substance used to give a permanent color to 
animal or vegetable fibers, and especially to cloth. The 
dyes which have been longest known are natural substances 
of vegetable or animal origin, cochineal being, however, al- 
most the only well-known dyestuff of the latter class. Dur- 



48 O ORGANIC CHEMISTRY. 

ing the last fifty years several of the most valuable natural 
dyes have been produced artificially. The most important 
of these are alizarin (p. 212) and indigo (p. 247). In addi- 
tion to this, new dyes of almost every conceivable color and 
shade have been prepared, chiefly from coal-tar products. 
The first commercial dye of this kind was prepared by 
W. H. Perkin, Sr., in 1857, by the oxidation of an impure 
aniline sulphate. This led to the popular designation of the 
dyes as " aniline colors;" and the name still clings to them 
in common usage, though it is not accurate from a scientific 
standpoint. 

The coal-tar dyes have acquired so great a commercial 
importance that they have been studied with extreme care, 
both from the scientific and from the technical standpoint. 
The special literature devoted to the subject is large,* and 
only the most elementary principles can be touched upon 
here. 

Chromophore Groups — It has been found that certain groups 
almost or quite always give a color to the substances contain- 
ing them. These are called " chromophore " groups (Witt, 
Ber. 9, 522; 21, 325.) The best known of them are the 
nitro group, N0 2 , the azo group, — N = N — , and the quinoid 
group, 

CH = CH 

/ \ 

= C C = . 

\ / 

CH = CH 

Auxochrome Groups The presence of a" chromophore " 

group does not, however, make the substance containing it a 

* See especially Schultz, Chemie der Steinkohlentheers; Nietzki, Chemie der organ- 
ischen Farbstoffe ; Schultz und Julius, Tabellarische Uebersicht der kiinstlichen or- 
ganischen Farbstoffe. An English translation of the last has been published by 
Macmillan and Co. 



OTHER AUXILIARY GROUPS. 48 1 

dyestuff. Thus, azobenzene, C C H 5 — N = N — C 6 H 5 , is deeply 
colored, but it is not a dye. To make the body a dye it must 
also contain some acid or basic group which will enable it to 
combine with the fiber or mordant. These are called " auxo- 
chrome " groups. The most important of them are the 
hydroxyl (phenol) 4 and the. amino groups. 

Mordants. — It is' often ^necessary to use with a dye some 
substance known as a il mordant," which shall combine with 
it, rendering it insoluble, and fixing it in the fiber. For 
basic dyes, the mordants most often used are tannic acid, 
with or without sQme preparation of antimony, and for acid 
dyes, acetates of -aluminium, chromium, or iron. These last 
are hydrolyzed byvwater, giving aluminium, chromium or 
iron hydroxide, which combines with the dye. In some 
cases the mordant used has an important effect in changing 
the shade or color produced by the dye (p. 213). 

Substantive and Adjective Dyes Dyes which will combine 

with fibers, and color them permanently without the use of 
a mordant, are said to be " substantive " ; those requiring 
a mordant are called " adjective." " Substantive "dyes for 
wool and silk are much more often found than for cotton or 
linen. The " congo " dyes (p. 475) have been mentioned as 
having special value because they are " substantive " for 
vegetable fibers. 

Other Auxiliary Groups Besides the chromophore and 

auxochrome groups, the presence of other groups in a dyestuff 
may be important. Thus a sulpho group may render the 
dye soluble, especially in the form of a salt. In some such 
cases a solution of the salt is used in the dyeing-vat, and the 
free sulphonic acid is precipitated in the fiber by the action 
of acid sodium sulphate. In a somewhat similar manner 



482 ORGANIC CHEMISTRY. 

indigo is sometimes fixed in a fiber by the reduction of o-nitro 
phenylpropiolic acid with glucose (p. 247), and azo com- 
pounds are prepared by treating the fiber successively with 
their components. 

Fast Colors Another very important property of dyes is 

as to whether they are " fast " or not ; that is, whether they 
are permanent when subjected to various kinds of treatment. 
Thus, dyes are distinguished as " wash-fast," " soap-fast," 
" alkali-fast," and " light-fast." Dyes which fade rapidly on 
exposure to the sunlight are called "fugitive." Probably 
no dye containing a carbon compound is absolutely perma- 
nent in the sunlight. 

Note. — In studying this chapter the student will find it use- 
ful to refer to the classification of compounds given in Chapter 
IX. 

Laboratory Exercises. 
Preparation of the following compounds : 

1. Benzene diazonium chloride (diazobenzene chloride). 

2. Aminoazobenzene. 

3. Sulphobenzene-azo-a-naphthylamine. 

4. Hydrazobenzene. 

5. Azobenzene. 

6. Benzidine. 

7. Phenylhydrazine. 

8. Glucosazone. 

9. Semicarbazine. 



SULPHUR COMPOUNDS. 483 



. CHAPTER XXII. 
SULPHUR COMPOUNDS. 

Mercaptans or Thioalcohols. 

The mercaptans may be considered as alcohols in which 
oxygen has been replaced by sulphur. They have the 
general formula, R-S-H, and may be prepared from alkyl 
halides and potassium hydrosulphide, from alcohols and 
phosphorus pentasulphide, and by the reduction of sulpho- 
chlorides : 

C 2 H 5 C1 + KSH = C 2 H 5 SH + KC1. 

Ethyl mercaptan. 

C 6 H 5 S0 3 C1 + 6H- C C H 5 SH + 2 H 2 + HC1. 

Benzene sulphochloride. Thiophenol. 

The reaction with phosphorus pentasulphide is complex, 
and gives poor yields. 

The mercaptans are mostly liquids with penetrating and 
excessively disagreeable odors. As is to be expected from 
the relation between water and hydrogen sulphide, they 
have slight acid properties. With mercury, especially, they 
form well defined salts (R— S) 2 Hg, and this fact gives to 
them their name mercaptan. Nitric acid oxidizes them to 
sulphonic acids : 

C 6 H 5 SH + 30 = C 2 H 5 S0 2 OH. 

Ethyl mercaptan. Ethyl sulphonic acid. 

Ethyl Mercaptan (ethanethiol) , C 2 H 5 SH, is prepared on a 
large scale from ethyl chloride and potassium hydrosulphide. 



484 ORGANIC CHEMISTRY. 

It boils at '36. 2°, and has a specific gravity of 0.83907 at 

20° . .... 

—5-. Its odor is so penetrating that it is possible to de- 
4 

tect 4J0000001 m S- by that means, an amount 250 times 
smaller than the smallest amount of sodium which can be 
identified by the spectroscope. Ethyl mercaptan is manufac- 
tured commercially for use in making " sulfonal " (p. 486). 
The factory is placed in as secluded a place as possible, but 
the odor causes trouble at a very considerable distance. 

Thiophenol (phenthiol), C 6 H 5 SH, can be prepared by the 
reduction of phenylsulphonic chloride (see above). It boils 
at 172. 5 , and has a disagreeable odor. It forms salts with 
mercury, lead, silver, and other metals, and gives phenyl 
disulphide (C G H 5 ) 2 S 2 with very mild oxidizing agents. 



Sulphides or Sulphur Ethers. 

The sulphur ethers are prepared by treating metallic sul- 
phides with alkyl halides : 

2 C 2 H 5 I + K 2 S = (C 2 H 5 ) 2 S + 2 KI. 

Ethyl sulphide. 

Mixed sulphides, corresponding to the mixed ethers, can 
be prepared by treating sodium salts of the mercaptans 
with alkyl iodides : 

C 2 H 5 SNa + CH 3 I = C 2 H 5 -S-CH 3 + NaI. 

Ethyl methyl sulphide. 

Ethyl Sulphide, (C 2 H 5 ) 2 S, is prepared from potassium sul- 
phide and ethyl chloride, or by distilling mercury mer- 
captide : 

(C 2 H 5 S) 2 Hg=(C 2 H 5 ) 2 S + HgS. 

Ethyl sulphide is insoluble in water, and has a disagree- 
able odor. It boils at 92 — 93 . It is worthy of notice that 



PHENYL SULPHIDE. 485 

while ethyl mercaptan has a lower boiling point than alcohol, 
ethyl sulphide has a very much higher boiling point than 
ether. These facts are doubtless connected with the asso- 
ciation of alcohol to more complex molecules, while ether 
and ethyl mercaptan do not so associate (Ramsay and 
Shields, Zeit. phys.Ch. 12, 465 and 468). 

Acetone Ethylmercaptol (dithioethyldimethylmethane), 

CH 3 /SC 2 H 5 

CHa \SC 2 H 5 ' 
is prepared by passing hydrochloric acid gas into a mixture 
of acetone and ethyl mercaptan. It is a liquid, boiling with 
some decomposition at i9o -ic)i and is manufactured for 
use in preparing sulfonal (p. 486). 

Phenyl Sulphide, (C 6 H 5 ) 2 S, is prepared by distilling lead 
thiophenolate, 

(C 6 H 6 S) 2 Pb = (C 6 H 6 ) 3 S + PbS. 

It is a liquid with a disagreeable odor, and boils at 292 - 
294 . 

While oxygen shows only a slight tendency to add ele- 
ments or groups and assume the quadrivalent form (see Am. 
Chem. J. 27, 311) sulphur exhibits, in a very marked degree, 
the tendency to become either quadrivalent or sexivalent. 
As a result of this property of sulphur, the mercaptans may 
be oxidized to sulphonic acids, the sulphides may be oxi- 
dized to sulphoxides and sulphones, and the sulphides and 
alkyl iodides form sulphonium compounds. 

C 2 H 5 SH-»C 2 H 5 -S = 

\OH. 

Ethyl mercaptan. Ethyl sulphonic acid. 

C 2 H 5 -S-C 2 H 5 -»^ 5 >S = 0. 

Ethyl sulphide. Diethyl sulphoxide. 



486 ORGANIC CHEMISTRY. 

QH C 2 H .0 

Ethyl sulphide. Diethyl sulphone. 

CH 5 C 2 H 5 .C 2 H 5 

CH 5 >b ~ > C 2 H 5 >b< I * 

Triethyl sulphonium iodide. 

Of these compounds, the sulphones and sulphonium bases 
will be considered first, as being more closely related to the 
sulphides. 

Sulphones. 

Diethylsulphone ^ 2 TT 5 >S , is prepared by oxidizing 

ethyl sulphide (C 2 H 5 ) 2 S, with fuming nitric acid. It crystal- 
lizes in rhombic plates, which melt at 70 , and boil without 
decomposition at 248°. It dissolves in 6.4 parts of water 
at 1 6°. It is neither acid nor basic in its properties. 

Diethylsulphone-dimethylmethane (" sulfonal "), 

CH 3 S0 2 C 2 H 6 

CH^ S0 2 C 2 H 5 ' 

is prepared by oxidizing dithioethyldimethylmethane with 
potassium permanganate. It melts at 125 - 126°, and boils 
with slight decomposition at 300 . It dissolves in 15 parts 
of boiling water, or in 500 parts of water at 16 . It is very 
stable toward either oxidizing or reducing agents. Sulfonal 
is used as a soporific agent. 

is treated with sulphur trioxide, by the oxidation of di- 
phenylsulphide, and by treating benzene sulphochloride, 
C 6 H 5 S0 2 C1, with benzene and aluminium chloride. It melts 
at i28°-i29°, and boils at 3 7 8°. It is decomposed by phos- 



Diphenylsulphone, (C 6 H 5 ) 2 S sX _ , is formed when benzene 



METHYLETHYLTHETIN BROMIDE. 487 

phorus pentachloride, giving chlorbenzene and benzene sul- 
phochloride : 

(C 6 H 5 ) 2 S0 2 + PC1 5 = C 6 H 5 C1 + C 6 H 5 S0 2 C1 + PC1 3 . 

Sjjlphonium Bases. 

As a nitrogen atom may combine with four alkyl groups, 
to form a group which unites with hydroxyl, giving a strong 
base, so a sulphur atom may combine with three alkyl 
groups and hydroxyl to form a sulphonium base. 

Triethyl Sulphonium Iodide, (C 2 H 5 ) 3 SI, is prepared by treat- 
ing ethyl suphide with ethyl iodide : 

Oft c . r tt t_^2^5. q .C 2 H 5 
C 2 H 5 >S + QH5l -C 2 H 5 >S< l • 

The iodide crystallizes in rhombic leaflets which are 
easily soluble. When heated, it decomposes into ethyl sul- 
phide and ethyl iodide, as tetrethyl ammonium iodide de- 
composes into triethyl amine and ethyl iodide, and as 
ammonium chloride decomposes into ammonia and hydro- 
chloric acid. 

(C 2 H 5 ) 3 SI = (C 2 H 5 ) 2 S-fC 2 H 5 I. 

When the iodide is treated with silver oxide and water it 

gives triethyl sulphonium hydroxide, (C 2 H 5 ) 3 SOH, which is 

easily soluble in water and is a strong base, forming salts 

readily with acids. 

C H CH CO FT 

Methylethylthetin Bromide, 2 5 >S< 2 2 . Alkyl 

v^ -H-3 _t>r 

sulphides combine directly with bromacetic acid to form 

thetin compounds of which methylethylthetin bromide is 

typical. The corresponding bases are weaker than the simple 

sulphonium bases, because of the acid group which they con- 



488 ORGANIC CHEMISTRY. 

„ r 7 z 7 7 ■ C > H 5 n CH.,C0 2 H , ' . , 

tarn. Methyletliyltlietin, _ >S<„~ , has acquired 

Lrl 3 (Jxi 

a special interest from the fact that by means of its brom- 

C 2 H 5 CH 2 C0 2 H . , 1 

camphorsulphonate, " > s <o^ r- TT r> r\> lt: nas been 
Crlg bU 3 — U 10 rl 14 br(J 

separated into optically active components (Pope and Peachy,- 
/. Chem. Soc. [London] 77, 1072). The asymmetry of the 
compound must be due to the sulphur atom, and its exis- 
tence furnishes additional evidence that the four groups are 

combined directly with the sulphur. A somewhat similar 

r it p Tr- 

active compound of tin, * 5 > Sn< 3 7 , has also been 

CH 3 1 

prepared by the same investigators. The discovery of these 
active compounds demonstrates that optical activity is not 
necessarily dependent on the single element carbon. 



Sulphonic Acids. 

The preparation of sulphonic acids by the oxidation of 
mercaptans, or sulphur alcohols, has already been referred 
to. This method of preparation is especially useful in the 
aliphatic series. In the aromatic series, on the other hand, 
sulphonic acids are prepared by treating compounds with 
concentrated sulphuric acid, or, in some cases, with fuming 
sulphuric acid or sulphur trioxide: 

C 6 H C + H 2 S0 4 = C 6 H 5 S0 2 OH + H 2 0. 

Benzene sulphonic acid. 

The presence of alkyl groups (as in toluene, C 6 H 5 CH 3 , 
xylene, C 6 H 4 (CH 3 ) 2 , etc.) or of hydroxyl or amino groups, 
causes aromatic compounds to be more easily attacked by 
sulphuric acid, and the sulphonic acid derivatives of such 
bodies may be obtained by the use of concentrated sulphuric 
acid alone, in many cases. When carboxyl, a nitro group, 



STRUCTURE OF THE SULPHONIC GROUP. 489 

or a sulphonic acid group is present, the sulphonic radical 
enters with greater difficulty, and a fuming acid is required. 
The position taken by the sulphonic acid group with re- 
gard to other groups, in aromatic compounds, is subject to 
the same rules as those which apply to the nitro group 

(P- 4I3)- 

Structure of the Sulphonic Group The structure of the 

group is established by the following facts : 

1. Treatment of salts of sulphonic acids with phosphorus 
pentachloride gives sulphonic chlorides : 

C 6 H 5 S0 3 Na + PC1 5 = C 6 H 5 S0 2 C1 + NaCl + POCl 3 . 

Sodium benzene Benzene sulphonic 

sulphonate. chloride. 

This demonstrates the presence of a hydroxyl group in 
the sulphonic acid, C G H 5 S0 2 OH. 

2. Sulphonic chlorides may be reduced to mercaptans, 
and mercaptans may, in turn, be oxidized to sulphonic acids: 

C 6 H 5 S0 2 C1 + 6H = C 6 H 5 SH + H CI + 2 H 2 0. 

Benzene sulphonic Thiophenol. 

chl oride . 

C 6 H 5 SH + 30 = C 6 H 5 S0 2 OH. 

These reactions indicate that the sulphur atom of the 
sulphonic acid is combined directly with carbon. 

If we assume, as seems altogether probable, that sulphuric 
acid and carbonic acid each contain two hydroxyl groups, 
the relation of sulphonic acids to sulphuric acid is very 
closely analogous to the relation of ordinary organic acids 
to carbonic acid. 

so< OH so< CA 

bU 2 < QH io «< H 

Sulphuric acid. Ethyl sulphonic acid. 



490 ORGANIC CHEMISTRY. 

/".^ OH C 9 Hr 

CO< OH CO< OH" 

Carbonic acid. Propionic acid. 

The sulphonic acids are isomeric with the acid esters of 
sulphurous acid. But while the esters are easily saponified 
by boiling with water or alkalies, the sulphonic acids are 
very stable in most cases. They are decomposed by fusion 
with caustic potash, however, and some of them are de- 
composed by heating with concentrated hydrochloric or 
sulphuric acid : 

C 6 H 5 S0 2 OK + KOH = C 6 H 5 OH + K 2 S0 3 . 

Phenol. 

C 6 H 4 <g^ 3 OH +HCl + H 2 = C 6 H 5 CH 3 + H 2 S0 4 +HCL 

Toluene sulphonic acid. Toluene. 

The last reaction is often useful for the regeneration of 
hydrocarbons, or other compounds, from the sulphonic 
acids. 

The sulphonic acids are generally easily soluble in water, 
are strong acids, and form very stable salts. These facts 
render the sulphonic acid group very important as an " auxo- 
chrome " group in many dyestuffs (p. 480). Sulphonic acids 
are also important for the preparation of phenols (p. 146), 
alizarin (p. 212), and " saccharin " (see below). 

Ethyl Sulphonic Acid, C 2 H 5 S0 2 OH, is prepared by the 
oxidation of ethyl mercaptan with potassium permanganate. 
It is also formed by the treatment of potassium sulphite 
with ethyl iodide. This last reaction is most naturally 
interpreted by assuming an unsymmetrical structure for the 
sulphite. 



5 K+ C 2 H 6 I = S0 2 <£f 



S0 2 <^+C 2 H 6 I = S0 2 <^ Tr 5 fKI. 



The abnormal reactions of silver nitrite (p. 411) and sil- 



SULPHO TOL UENE. 49 1 

ver cyanide (p. 306) render such a conclusion somewhat 
uncertain, however. 

Ethyl sulphonic acid forms a deliquescent, crystalline 
mass. A considerable number of stable salts are known ; 
also the chloride, C 2 H 5 S0 2 C1, and the amide, C 2 H 5 S0 2 NH 2 . 

Benzene Sulphonic Acid, C 6 H 5 S0 2 OH, is prepared by dis- 
solving benzene in fuming sulphuric acid, or by boiling 
benzene for some time with concentrated sulphuric acid. 
The free acid crystallizes in plates containing one molecule 
of water. It is very easily soluble in water. When its 
sodium salt is fused with potassium hydroxide, potassium 
phenolate, C 6 H 5 OK, is formed. When the same salt is 
heated with potassium cyanide, phenyl cyanide, C 6 H 5 CN, 
distills over. 

CH t 
o-Sulphotoluene, C e H 4 < * . 

When toluene is dissolved in concentrated sulphuric acid, a 
mixture of the ortho and para sulphonic acids is formed. 
The formation of the ortho acid seems to be favored by 
carrying on the reaction at a low temperature, but the para 
acid is always formed in larger amount than the ortho com- 
pound. By dilution, and treatment with calcium carbonate, 
the sulphuric acid forms calcium sulphate, which is difficultly 
soluble, while the sulphonic acids form calcium toluene 
sulphonates, 

(CeH^^Ca, 

which are easily soluble. After filtering, the calcium may 
be precipitated by potassium carbonate, leaving potassium 
sulphonates in solution. By treating the dry potassium 
salts with phosphorus pentachloride the sulphochlorides are 
obtained. 



49 2 ORGANIC CHEMISTRY. 

CH CTHT 

c « h *<so;ok +pci '= c « h '<so;ci +kci+poc1 *- 

Toluene sulphochloride. 

The ortho sulphochloride is liquid at ordinary tempera- 
tures, while the para compound is solid, and a partial sepa- 
ration can be based on this fact. 



o-Toluene Sulphamide, 



C 6 H 4 <° 



3 

^S0 2 NH 2 



When the impure liquid toluene sulphochloride mentioned 
above is treated with aqua ammonia, a mixture of the 
ortho and para sulphamides is obtained, from which the 
latter can be prepared pure by crystallization from water. 

c ^<sSci +2NHs = c ^<sJnh 2 + nh * ci 

Toluene sulphamide. 

o-Toluene sulphamide crystallizes in octahedra, which 
melt at 15 5 . 

Benzoic Sulphinide (saccharin), 

C H 4 <C°>NH. 

When o-toluene sulphamide is oxidized in a strongly alkaline 
solution by means of potassium ferricyanide, or potassium 
permanganate, the orthosulphamide of benzoic acid, 

C0 2 H 
6 4 ^S0 2 NH 2 ' 

is formed. This melts at i65°-i67°, and is not sweet. 
If the oxidation is conducted with potassium permanganate 
in a neutral or faintly alkaline solution, benzoic sulphinide, 

CO 
QH 4 < C ^>NH, 



ANTHRAQUlNOhlE-2-SULPHONlC ACID. 493 

is obtained. This is the imide of orthosulphobenzoic acid, 

C0 9 H 



C C H 4<( 



S0 2 OH' 

and is remarkable for its intensely sweet taste. The sweet- 
ness is variously estimated as being from 300 to 500 times 
that of cane sugar. It is known commercially as " sac- 
charin," and is manufactured in considerable quantities, 
partly for the use of patients suffering from diabetes, who 
are compelled to avoid the use of sugar, partly for use as 
an adulterant. It has no direct food value, and possesses 
antiseptic properties which interfere with digestion to some 
extent. It melts at 220 . 

Many other sulphinides are known. They all form well- 
defined salts in which the hydrogen of the imide group is re- 
placed by metals. 

Naphthalene Sulphonic Acids, C 10 H 7 SO 3 H. Both of the sul- 
phonic acids of naphthalene are formed when naphthalene is 
dissolved in concentrated sulphuric acid. The formation of 
the a-acid is favored by a low temperature (8o°), while that 
of the /3-acid is favored by a high temperature (160 ). The 
two acids may be separated by means of their lead or cal- 
cium salts. By fusion with caustic potash the acids are con- 
verted into a- and fi-naphthol, C 10 H 7 OH. 

Anthraquinone-2- sulphonic Acid, 

CO 
C 6 H 4 < > C c H 3 SOoH, 

is formed, together with some of the disulphonic acid, when 
anthraquinone is heated for some time with concentrated 
sulphuric acid at 2 5o°-2 6o°, or with a slightly fuming acid 
at 2oo°-2 3o°. If the cold solution is diluted, and salt is 
added, the sodium salt of the sulphonic acid is precipitated, 
a method of separation which can be applied in many other 



494 ORGANIC CHEMISTRY. 

cases. When the sodium salt is fused with potassium or 
sodium hydroxide, with the addition of some potassium 
chlorate, alizarin, 

CO 

C 6 H 4<co >C 6 H 2 (OH) 2 , 

is formed (p. 212). 

The Sulphonic Acid of Acetic Acid, 

is prepared by heating glacial acetic acid with the chloride 
of sulphuric acid : 



OH C0 2 H 

^Cl ~ U±l2< SOX>H 



CH 3 C0 2 H + S0 2 <_ =CH 2 < 00 ^ OTT + HC1. 

The acid crystallizes with one molecule of water. It 
melts at 75 , and forms both acid and neutral salts. 

Laboratory Exercises. 

Preparation of the following compounds : — 

1. Triethyl sulphonium iodide. 

2. Benzene sulphochloride. 

3. Benzoic sulphinide. 

4. Sulphanilic acid. 

5. Paranitrobenzoic sulphinide. 

6. Paraaminobenzoic sulphinide. 



THIOPHENE. 495 



CHAPTER XXIII. 
HETEROCYCLIC COMPOUNDS. 

Compounds which contain a ring composed of atoms of 
two or more kinds have been termed heterocyclic. A consid- 
erable number of such compounds have already received 
mention. To this class belong the anhydrides and imides of 
bibasic acids (pp. 277 and 289), lactones (p. 318), pyridine, 
(p. 437), and quinoline (p. 446), uric acid (p. 293), furfural 
(p. 360), and benzoic sulphinide. A large proportion of those 
alkaloids whose structure has been more or less completely 
determined, also have a heterocyclic structure. Some of 
these will be mentioned briefly in the following chapter. 
Only a few of the many other heterocyclic compounds re- 
quire special mention here. 

Thiophene, QH 4 S, and its homologues, thiotoluene, 
C 4 H 3 SCH 3 , and 1, 4-thioxene, are found in coal-tar, and 
are always present in the benzene, toluene, and xylene 
from that source, unless the latter have been specially 
purified to remove them. When mixed with a little isatine, 

C,H 4 <^>CO, 

and concentrated sulphuric acid, they give a beautiful blue 
color. This is called the indophenin reaction ; and the fact 
that benzene from coal-tar gives this reaction, while pure 
benzene from benzoic acid or other sources does not give it, 
caused Victor Meyer to look for the reason of this difference, 
and led to the discovery of thiophene (1883) (Ber. d. chem. 



496 ORGANIC CHEMISTRY. 

Ges. 16, 1465). V. Meyer suggested that thiophene is ben- 
zene in which the bivalent group — CH = CH— is replaced 
by a sulphur atom, thus, 

CH = CH 
I >S. 

CH = CH 

This view was confirmed when Volhard and Erdmann pre- 
pared thiophene synthetically by heating sodium succinate 
with phosphorus trisulphide (Ber. d. chem. Ges. 18, 454). 

CH 2 -C0 2 Na CH = CH 

I + I >s. 

CH 2 -C0 2 Na CH = CH 

Thiophene boils at 84 , and has a specific gravity of 

1.0705 at — - • While thiophene is somewhat less stable 

than benzene, especially toward oxidizing agents, it exhibits 
a remarkable resemblance to that hydrocarbon in many of 
its properties and in its derivatives. Chlorine, bromine, and 
nitro substitution products, sulphonic acids, and carboxylic 
acids are known in considerable number. The development 
of the chemistry of thiophene is one of the interesting chap- 
ters in the history of organic chemistry, and it can be easily 
followed in the papers which appeared within a few years 
after V. Meyer's discovery. 

Coumarin, 

CH = CH 

QH ' I . 

^O-CO 

When salicylic aldehyde, 

CHO 



C 6 H 4 < 



OH ' 



PYRAZOLE. 497 

acetic anhydride, and sodium acetate are heated together 
acet-o-coumaric acid, 

CH = CH-C0 2 H 
^ 6 4< 0-C 2 H 3 

is formed. This yields coumarin when heated. The syn- 
thesis is of especial interest because it was the first appli- 
cation of the well-known and important Perkin's synthesis 
(p. 244). Coumarin melts at 67 , and boils at 290 . It 
is found in tonka beans and Asperula odorata. It has a 
pleasant odor, and is used in perfumery for the preparation 
of the Asperula essence. 

Coumarone, 

CeH4 \ o ^ CH ' 

is formed by the action of alcoholic potash upon coumarin 
dibromide, or upon a-bromcoumarin. 

CH = CBr koh • ^H 

QH ' I ~> C 6 H ' ^C-C0 2 H 

x O -CO x O x 

a-Bromcoumarin. Coumarilic acid. 

->C,H 4 ( C H )CH. 

Coumarone. 

The reaction is evidently somewhat related to the decom- 
position of /3-brom acids when treated with sodium carbonate 
(p. 393). Coumarone boils at 172 . 

Pyrazole, 

NH-N 
ch' II , 

^CH-CH 

is formed when a mixture of epichlorhydrin and hydrazine 
hydrate is warmed, at first alone, and then with the addition 
of zinc chloride, which acts as a condensing agent. 



49 8 ORGANIC CHEMISTRY. 



CH 2 


CI 








1 




NH 2 


y NH- 


-N 


CH 


+ 


2 1 = 


= CH 


II 


1 


>o 


NH 2 


^CH- 


-CH 


CH 2 











+ H 2 + NH 4 C1+NH 3 . 



Pyrazole crystallizes in needles, which melt at 70 . It 
boils at 1 86-1 88°. It is easily soluble in water, alcohol, 
ether, and benzene. The aqueous solution is neutral, but 
pyrazole forms well-defined salts, of which the chloride, 
C 3 H 4 N 2 HC1, and the chlorplatinate, (C 3 H 4 N 2 ) 2 H 2 PtCl 6 + 
2H 2 0, may be considered as types. 

i-Phenylpyrazole, 

/ N -CH 

QH 5 N I , 

\CH=CH 

is formed from phenylhydrazine, C 6 H 5 NHNH 2 and epichlor- 
hydrin. It melts at n°, and boils at 246. 5 . 

Pyrazolone, /NH-NH 

CH I , 

^ CH-CO 

is formed when hydrazine sulphate and sodium formyl ace- 
tic ester are warmed with a normal solution of sodium 
hydroxide. 

NH 2 NH 2 H 2 S0 4 + H-CO-CHNaC0 2 C 2 H 5 + NaOH 

Hydrazine sulphate. Sodium formylacetic ester. 

NH-NH 

/ 
= CH + Na 2 S0 4 +C 2 H 5 OH + 2H 2 0. 

CH-CO 

Pyrazolone crystallizes from toluene in needles which melt 
at 165 . It is easily soluble in alcohol and water, difficultly 
soluble in ether. It is not basic in character. 



ACRIDINE. 499 

i-Phenyl-3-methylpyrazolone, 

/CO-CKj 
C 6 H 5 -N I 

\ N =C-CH 3 

When acetacetic ester and phenylhydrazine are mixed in 
molecular proportions they condense to a hydrazone, 

CH, 



C 6 H 5 -NHN = C< 



CH 2 C0 2 C 2 H 5 



On warming this for some time, it condenses further, with 
loss of alcohol, forming i-phenyl-3-methylpyrazolone. This 
crystallizes from water in prisms which melt at 127 . It 
boils at 2 8 7 under a pressure of 205 mm. Phenyl methyl- 
pyrazolone forms salts both with acids and with bases. The 
silver salt is AgC 10 H 9 N 2 O, the hydrochloride, C 10 H 10 N 2 O- 
HC1 + H 2 0. 

i-Phenyl-2 , 3-dimethylpyrazolone (antipyrine) , 

/CO CH 

QH 5 -N || , 

\N(CH 3 )-C-CH 3 

is formed when i-phenyl-3-methylpyrazolone is heated in a 
sealed tube to ioo°-i2o° with methyl iodide, caustic potash, 
and methyl alcohol. Antipyrine crystallizes from toluene in 
leaflets, which melt at 11 6°. It is a monacid base. The 
salts are, mostly, easily soluble in water. Antipyrine is used 
in medicine as an antipyretic. 

Acridine, 

/CH X 
QH 4 I C 6 H 4 , 

x N y 

may be considered as anthracene in which a CH group has 
been replaced by a nitrogen atom. It is formed when 



500 ORGANIC CHEMISTRY. 

formyl diphenyl amine is heated with zinc chloride, or when 
diphenyl amine is heated with crystallized oxalic acid and 
zinc chloride : 

C 6 H 5 | C 6 H 5 = C 6 H 4 | C 6 H 4 +H 2 0. 

H-C=0 X CH/ 

The reaction is of somewhat more than usual interest, 
since it indicates very clearly that acridine contains a para 
union between the nitrogen and carbon atoms of the central 
nucleus, and, by analogy, points to a similar structure for 
anthracene. Acridine is also found in coal-tar. It is a 
very stable substance, melting at 107 , and boiling at a tem- 
perature above 360 , without decomposition. It is a weak 
base. Potassium permanganate oxidizes it to acridic acid 
(2, yquinoline dicarboxylic arid), 



CO 



C0 2 H 
C0 2 H 



N 



CO 
Acridone, C 6 H 4 < ATTT > C 6 H 4 , may be prepared by the 
NH 

oxidation of acridine with bleaching powder and cobalt 

nitrate. It is also formed when o-aminobenzophenone, 

/CO-C 6 H 5 

tfi 4 \NH 2 

is heated to 35 5 with lead oxide. Acridone crystallizes in 
needles, which melt at 3 5 4 . By distilling with zinc dust it 
is reduced to acridine. 

Other heterocyclic compounds in great numbers, and of a 
great variety of types, are known. Some of those given are 
no more important than others which might have been 
selected. It does not seem advisable, however, to extend 



LABORATORY EXERCISES. 5<DI 

the list, as it is not possible, in a work of the present scope, 
to include representatives of all of the types which have 
been discovered. 

Laboratory Exercises. 

Preparation of the following compounds: — 

i. Thiophene. 
2. Antipyrine. 



502 ORGANIC CHEMISTRY. 



CHAPTER XXIV. 
ALKALOIDS. 

Many plants contain basic compounds of nitrogen to 
which the general name alkaloids has been given. The 
plants containing such compounds belong almost exclusively 
to the class of dicotyledons. In many cases the same plant 
contains several different alkaloids ; but, when this is the 
case, the different bases are almost invariably closely related 
in structure. Different plants of the same family often con- 
tain the same or closely related alkaloids, while a given 
alkaloid is rarely found in plants belonging to different 
families. 

Most of the alkaloids exert a powerful physiological action 
on the animal organism. Many of them are valuable medi- 
cal agents, and some of them are very powerful poisons. 

Most of the alkaloids form, with acids, well characterised 
salts. In many cases they can be extracted from aqueous 
alkaline solutions by means of immiscible solvents, as ether, 
amyl alcohol, chloroform, or benzene, while acids, in turn, 
extract them from solution in such solvents. Many of 
the alkaloids give, with acids and other reagents, highly 
characteristic color reactions which are of great value in 
toxicology. All alkaloids give precipitates with phospho- 
molybdic and phosphotungstic acids, and many of them, 
with tannin and with potassium mercuric iodide. 

The alkaloids are generally optically active, and are 
usually laevorotatory. 



PYRIDINE GROUP. 503 

The number of the alkaloids is very large, and many of 
them have been carefully studied and their structure estab- 
lished with a good degree of certainty. Only a very few 
have been prepared synthetically. They are best classified 
in accordance with the characteristic group which each 
contains. Only -a few of the more important can be 
mentioned. 

1. Pyridine Group. 
The alkaloids of this group are derivatives of pyridine, 
CH 

CH CH 

I! I • 

CH CH 

\ // 

N 

Pilocarpine, C u H 1G N 2 2 , is the most important alkaloid of 
Jaborandi leaves {Pilocarpus pentafolius). Its chloride is 
C n H 16 N 2 2 • HC1. The base somewhat resembles nicotine 
in its physiological properties. 

Coniine, C 8 H 17 N, the alkaloid of hemlock (Conium macu- 
la/um), has been considered (p. 435), as has also piperi?ie, 
C 17 H 19 N0 3 , the alkaloid of pepper (p. 434). The former 
is a monacid base, but the latter forms a chlorplatinate of 
the remarkable formula, 

(C 17 H 19 N0 3 ) 4 .H 2 PtCl 6 . 

Nicotine (C 10 H 14 N 2 ), the principal alkaloid of tobacco (see 
p. 438), is sixteen times more poisonous than coniine. 

Atropine, C 17 H 23 N0 3 , is the chief alkaloid of the deadly 
nightshade, Atropa belladonna, and is found also in Datura 



504 ORGANIC CHEMISTRY. 

stramonium and in several other plants. Atropine is a 
powerful poison. It causes a widening of the pnpil of the 
eye, and is often used by oculists for that purpose. This 
effect is called mydriasis, and is also produced by some other 
alkaloids, and by some artificial bases. Atropine is a raon- 
acid base. 

Cocaine, C 17 H 21 N0 4 , is found in cocoa leaves {Erythroxo- 
lon coca). It is a monacid base. Cocaine is much used to 
produce local anaesthesia for surgical operations upon the 
eyes or teeth, but it is so poisonous that great care is re- 
quired in its administration. 

According to recent researches, atropine and cocaine are 
derivatives, not of pyridine, but of pyrrolidine, 

CH 2 -CH 
I >NH. 

CH 2 -CH 2 

Connection Between Structure and Physiologial Effect of Cocaine. 

— The structure assigned to cocaine is, 

CH 2 -CH CH-CO-OCH 3 

I I 

N - CH 3 CH - O - COC 6 H 5 . 

I I 

CH 2 — CH CH 2 

According to this formula, it is an ester of benzoic acid, 
C 6 H 5 COOH, and a study of other esters of that acid has 
led to the conclusion that its peculiar physiological action is 
dependent largely on that portion of its structure. This has 
led to the synthesis of two compounds which can replace 
cocaine for some purposes of local anaesthesia, but which 
are far less poisonous than that base. These are : 



QUINOLINE GROUP. 505 

The methyl ester of p-amino-o-hydroxy-benzoic acid (" Ortho- 
form "), 



C0 9 CH 3 1 
OH 2 

\NH 2 4 



C c H 3 -OH 



and the methyl ester of diethylglycocoll-aminosalicyclic acid 
(" Nervanine "), 

/NH-CO-CH 2 -N(C 2 H 5 ) 2 5 

QH3-OH 2 

\C0 2 CH 3 1 

(Einhorn, Ann. d. Chem. (Liebig), 311, 26 and 154). 

Ecgonine, C 9 H 15 N0 3 -f-H 2 0, is formed by the saponifica- 
tion of cocaine, either by dilute acids or by barium hydrox- 
ide. The structure is evident from the formula of cocaine. 
As an amino-acid it combines both with acids and with bases 
to form well-characterized salts. Other esters of ecgonine 
are found along with cocaine in cocoa-leaves. The ecgonine 
can be obtained from these by saponification, and can be 
then converted into cocaine, — facts of very considerable 
technical importance. 

2. Quinoline Group. 

The alkaloids of this group are derivatives of quinoline, 

CH CH 

// \ / ^ 
CH C CH 

I II I 

CH C CH 

^ / \ // 
CH N 

Quinine, C 20 H 24 N 2 O 2 , is the most important alkaloid of 
" Peruvian bark," the bark of several varieties of trees 



506 ORGANIC CHEMISTRY. 

belonging to the genus Cinchona. It forms salts with one or 
with two molecules of a bibasic acid. The former are called 
the neutral salts, as the latter have an acid reaction. The 
"neutral" sulphate, (C 20 H 24 N 2 O 2 ) 2 H 2 SO 4 +8H 2 O (or, crys- 
tallized from alcohol, with 2H 2 0), is much used in medicine 
as an antipyretic. It is a specific in cases of malarial fever. 

Cinchonine, C^H^N^O, is usually, if not always, associated 
with quinine. It possesses similar chemical properties, and 
has a similar physiological effect. 

Quinidine, C 20 H 24 N 2 O 2 , and cinchonidine, C 19 H 22 N 2 2 , are 
isomeric with quinine and cinchonine, and can be prepared 
from them by a molecular rearrangement. They are also 
found in nature. 

Strychnine, C 21 H 22 N 2 2 , is found in St. Ignatius' bean, 
in Strychnos mix vomica, and in some other plants. Strych- 
nine has an intensely bitter taste. It is a violent poison, 30 
milligrams being a fatal dose. In very small doses it acts 
as a powerful stimulant, in larger doses it produces tetanus. 

Brucine, C 23 H 26 N 2 4 , is always found with strychnine in 
plants, and is probably closely related to it in structure. It 
resembles strychnine in its physiological effects, but is a less 
violent poison. 

3. ISOQUINOLINE GROUP. 

The alkaloids of this group are derivatives of isoquinoline, 

CH CH 

* \ / % 

CH C CH. 

I II I 

CH C N 

% / \ // 
CH CH 



BERBERINE. 507 

When incisions are made in the green seed capsules of 
the white poppy {Pap aver somniferum P), a milk-like sap 
exudes, which dries to a gummy mass, and is called opium. 
Opium contains a number of alkaloids, of which the most im- 
portant, with their average proportion, are the following : 

Morphine, C 17 H 19 NO,+H 2 .... 10 per cent 

Narcotine, C 22 H 23 N0 7 6 

Papaverine, C 20 H 21 NO 4 1 

Codeine, C 18 H 21 N0 3 0.3 

Narceine, C 23 H 27 N0 8 +3H 2 .... 0.2 
Thebai'ne, C 19 H 21 N0 3 0.15 

Of these alkaloids only narcotine, papaverine, and nar- 
ceine are derivatives of isoquinoline, while morphine, 
codeine, and thebai'ne are derivatives of phenanthrene. 

All of these alkaloids are monacid bases, and all produce 
a hypnotic effect, though the different individuals vary 
greatly in power. Morphine and codeine are most used in 
medicine. 

Laudanum is an alcoholic extract of opium. Paregoric is a 
more dilute extract of opium, containing also camphor. 

Hydrastine, C 21 H 21 N0 6 , is the principal alkaloid of golden 
seal {Hydrastis Canadensis Z.). It has a strong styptic 
effect, causing a contraction of the blood-vessels. It is 
a monacid base. 

Berberine, C 20 H 17 NO 4 , is also found in golden seal, and 
is found in a considerable number of other plants. It 
crystallizes in yellowish brown needles, and its aqueous solu- 
tion is yellow, while almost all other pure alkaloids are 
colorless. It is a monacid base. Berberine has a toxic 
effect on dogs, producing paresis and interfering with the 
respiration. Upon men it seems to have little toxic effect, 
even in considerable doses. 



508 ORGANIC CHEMISTRY. 

4. Alkaloids of Unknown Structure. 

Veratrine, C 37 H 53 NO n , is a poisonous alkaloid found in 
white hellebore (Veratrum album), and in sabadilla seeds 
( Veratrum sabadilla). 

Jervine, C 26 H 37 N0 3 , is found in the same plants, and 
especially in white hellebore. It also is a violent poison. 

Gelsemine, C 22 H 26 N 2 3 , is an alkaloid found in the yellow 
jasmine (Gelsemium sempervirens). It is a monacid base. 
Its poisonous effects resemble those of strychnine in part, 
and partly those of curarine, the alkaloid of " curare," a 
substance used by the Indians of South America in poison- 
ing their arrows. 

Aconitine, C 34 H 47 NO n , is the alkaloid of aconite (Aconi- 
tum napellus). It is one of the most violent poisons. In 
very minute quantity it produces a prickly sensation on 
the tongue. It widens the pupil of the eye in the same 
manner as atropine. 

Emetine, C 30 H 40 N 2 O 5 , is the chief active principle of 
ipecac (Cephailio Ipecacuanha). It is a diacid base. Its 
emetic effect depends on the local irritation which it causes. 

Lobeline, C 18 H 23 N0 2 , is found in Lobelia inflata. The 
pure alkaloid is a viscous liquid having a yellow color. As 
a poison it affects the respiratory organs, inhibiting their 
action. 

Solanine, C 52 H 93 N0 18 . See p. 378. 



Laboratory Exercises. 

Study the general alkaloidal reactions, and the reactions used 
for the identification of some of the more important alkaloids. 



PROTEINS. 509 



1 CHAPTER XXV. 

COMPOUNDS OF INTEREST IN PHYSIOLOGY 
AND IN PATHOLOGY. 

Proteins. — Under this general term is included a large 
class of nitrogenous bodies which appear to be more inti- 
mately associated with the life processes than any other com- 
pounds. They all contain carbon, hydrogen, nitrogen, and 
oxygen ; very many contain sulphur, and some contain phos- 
phorus and iron. 

Classification The following classification is that of 

Cohnheim.* Only the more important of the compounds 
mentioned in the classification can be considered here, and 
those very briefly. 

I. True Albuminous Bodies. 

1. Albumins. 

Serum albumin, egg albumin, lactalbumin. 

2. Globulins. 

Serum globulin, egg globuli//, lacioglobulin, cell globulins, 
plant globulins. 

3. Coagulating albumins. 

Fibrinogen, myosin, myogen, gluten protein. 

4. Nucleoalbumins. 

Casein, vitellin, phytovitellin, nucleoalbumins of the cell 
protoplasm, mucous nucleoabumiiis. 

II. Transformation Products (Proteoses). 

1. Acid albumins and alkali albuminates. 

2. Albumoses, peptones, and allied bodies. 

* Chemie der Eiweisskbrper, S. 82. 



5IO ORGANIC CHEMISTRY. 

III. Proteids* 

i. Nucleoprotei'ds. 

Compounds of the nucleic acids with, a. Histone, b. Pro- 
tamine, c. Other albumins. 

2. Haemoglobins. 

Compounds of histone with haematin. 

3. Glycoproteins. 

Compounds of albumin with glucosamine and other car- 
bohydrates. 
Mucin, mucoid, helicoproteid. 

IV. Albuminoids. 

1. Collagen. 

2. Keratin. 

3. Elastin. 

4. Spongin, fibrin, etc. 

5. Amyloid. 

6. Albumoid. 

7. Coloring matters derived from albumins. 

Albumins. — The composition of the albumins varies be- 
tween narrow limits and is, approximately, as follows : 



c . . 


• 53-o 


Per cent 


H . . 


. 7.0 


" " 


N . . 


. 16.0 


" " 


S . . 


. . 1.9 


" " 


O . . 


. 22.1 


" " 



For the albumin from the white of an egg the formula 
C 72 H 112 N 18 S0 22 has been given, but the formula cannot be 
considered as established or important. This formula gives 
a molecular weight of 161 2. Determinations by the freez- 
ing-point method have given, approximately, 15,000. Os- 
borne has recently discussed the question on the basis of 

* The term " proteid " is used by many English writers in the sense given to the 
word protein above. The classification here given corresponds to the German usage. 



ALBUMINS. 5 1 1 

the amount and character of the sulphur piesent, and gives 
evidence in support of a similar value for the molecular 
weight. He also assigns definite formulae to a considerable 
number of the proteins (/. Am. Chem. Soc. 24, 160). 

The molecule is evidently extremely large and complex ; 
and it is altogether possible, perhaps probable, that the dif- 
ferent molecules composing a given albumin, as egg albumin, 
or serum albumin (from the clear, watery fluid of the blood), 
are not all alike. It seems likely that the molecules of albu- 
min combine easily with each other, and with other substances, 
to form more complex molecules, and that these, in turn, may 
decompose, or hydrolyze, giving new products. Such syn- 
theses and decompositions must be intimately associated 
with the life processes in the organism of the animal or 
plant. 

A very few of the albumins have been crystallized ; but 
even crystallization cannot be taken as proof of a homogene- 
ous, pure substance in this case, because of their very strong 
tendency to take up other substances (Kossel, Ber. d. chem. 
Ges. 34, 3229). 

The albumins are soluble in water, and are not precipi- 
tated by a small amount of acid or alkali, apparently because 
they possess both basic and acid properties. A larger 
amount of a mineral acid precipitates them, and they are also 
precipitated by heat when their solutions contain a neutral 
salt. 

When albumins are decomposed by the action of acids or 
bases, the most characteristic decomposition products are 
amino-acids. Of especial interest are the following sub- 
stances, the first two of which are derivatives of guanidine, 

/NH 2 
C = NH, 

\NH 2 



512 




ORGANIC CHEMISTRY. 








NH 2 












/ 








NH 2 




C = NH 


NH, 


-CH 2 


CH 2 NH 2 


/ 




\ 




1 


1 


C = NH 




NH-CH 2 




CH 2 


CH 2 


\ / 


CH 3 


1 




1 


1 


N 




CH 2 




CH 2 


CH 2 


\ 


CH 2 


1 




1 


1 




1 


CH 2 




CHNH 2 


CH 2 NH 2 



C0 9 H 



I 
CHNH 



I 
C0 9 H 



C0 2 H 

Creatine. Arginine. Ornithine. Putrescine. 

Lysine, or a,e-Diamino Caproic Acid, 

CH 2 NH 2 CH 2 CH 2 CH 2 CHN H 2 C0 2 H, 
histidine, C 6 H 9 N 3 2 , 

leucine, or amino caproic acid, a-aminoisocaproic acid, 



aspartic acid, 



CH ^>CH-CH 2 CH< C02 2 H , 
CHNH.-CO.H 



CH o -C0„H 



and glutaminic acid (a-aminoglutaric acid), 

CHNH 2 C0 2 H 
2< CH 2 C0 2 H 
are also obtained by the decomposition of albumins. 

In the animal body the most important decomposition 
products are urea, NH 2 

CO< NH 2 ' 
and uric acid (p. 293). 

Globulins. — These are insoluble in water, but are soluble 
in neutral salt solutions, and are reprecipitated on dilution. 
They are coagulated by heat. 



ALBUMOSES AND PEPTONES. 5 13 

Fibrin is the name given to the albuminous substance 
which separates from blood, and causes its coagulation, or 
clotting. If the blood is whipped with a stick or a glass rod 
as soon as it is drawn, the fibrin separates on the latter in 
shreds, and, after washing, is pure white. The formation of 
the fibrin in thexlotting of the blood is occasioned by the 
action of a fibrin ferment, or enzyme (see below), upon solu- 
ble fibri?ioge7i contained in the blood. 

Nucleoalbumins. — While the albumins are soluble, and are 
found in the fluids of the body, the nucleoalbumins are 
almost insoluble, and form a part of the protoplasm. They 
are found especially in the cells. They are somewhat acid 
in character, and are soluble in alkalies. 

Casein, or the curd of milk, belongs to the nucleoalbumin 
group. Whether the casein from different kinds of milk is 
identical or not has not been fully determined, but the caseins 
from different sources differ in some of their properties. 
The casein is in solution in normal milk, and is not coagu- 
lated by boiling. It is coagulated by dilute acids, and by 
the enzyme found in rennet. When some lactic acid has 
been formed by the fermentation, which always occurs in un- 
sterilized milk, the casein will coagulate on heating the milk. 

Albumoses and Peptones are formed by the action of proteo- 
lytic enzymes (pepsin and trypsin, see below) upon albumins, 
and other proteins. They have a much smaller molecular 
weight than the albumins, are easily soluble in water, are 
not coagulated by heat, and are not precipitated by acids or 
by potassium ferrocyanide. In the process of digestion they 
seem to be intermediate between the proteins of the food 
and those of the living body, being formed by the decompo- 
sition of the former, and, in turn, uniting with themselves, or 
with other substances, to form the latter. 



514 ORGANIC CHEMISTRY. 

Nucleoproteids are compounds of albumin with nucleic acid. 
Kossel and Lilienfeld give the following scheme for the 
composition and decomposition products of these compounds. 

Nucleoproteids 



Albumin Nuclei'n 

(Histone) 



Albumin. Nucleic acid. 

The nucleoproteids are found especially in the nuclei of 
the cells. According to the above scheme the nucleins are 
intermediate between the nucleoproteids and the nucleic acids. 
They are more acid than the former, and contain a much 
larger per cent of phosphorus. By proper treatment with 
alkalies, substances containing nucleoalbumins and nucleins 
give nucleic acids (See Levene, J. Am. Chem. Soc. 22, 329). 
The nucleic acids are themselves complex bodies, and give 
by their decomposition xanthine, 

HN-CO 

I I 

CO C-NH 
I II )CH, 

HN-C C y 

and its derivatives, phosphoric acid, and a carbohydrate. 

Haemoglobin is the chief coloring matter of the blood. It 
is also the substance which directly absorbs the oxygen of 
the air in the lungs, combining with it to form oxy haemo- 
globin. In the passage from the arterial to the venous sys- 
tem, through the capillaries, in the circulation of the blood, 
this absorbed oxygen enters into combination with other 
substances, oxidizing them, and thereby furnishing heat and 



E LAST INS. 515 

energy for the body. Haemoglobin contains iron, and both 
its color and its property of combining with oxygen are sup- 
posed to be due to this element. 

By means of acids haemoglobin is decomposed into globin 
and haematin. The latter is a coloring matter which con- 
tains iron, and can be separated in the form of its chloride, 
which is called haemin. 

Glycoproteids are albuminous bodies which give a carbohy- 
drate as one of their decomposition products. They are 
acid in character, are soluble in water, and are not coagu- 
lated by heat. The most important of them are mucin and 
mucoids. 

Collagens form the chief part of the organic matter of 
bones, and are also found in other portions of the body. 
By boiling with water, especially in the presence of a little 
acid, they are converted into gelatine. Gelatine absorbs 
cold water, and swells up, but does not dissolve. It dis- 
solves in hot water to a colloidal solution, which does not 
diffuse through parchment, and which solidifies on cooling, if 
not too dilute. 

Keratins form a principal constituent of the epidermis, 
hair, nails, hoofs, horns, and feathers. They contain sulphur, 
partly in so loose a state of combination that they give a 
precipitate of lead sulphide on boiling with an alkaline solu- 
tion of a lead salt. The albumin contained in the keratins 
gives, by its decomposition, a larger amount than usual of 

tyr ° Sin ' ■ ru CH.CHNH.CO.Hi 

^^OH 4 

Elastins are found in the connective tissue of the higher 
animals, and are especially abundant in the neckband (liga- 
mentum nachae). The sulphur which they contain is either 



516 ORGANIC CHEMISTRY. 

loosely combined, or is not an essential constituent (Chit- 
tenden and Hart, Zeit. f. Biologie, 25). 

Enzymes, or Soluble Ferments. 

The name enzyme is applied to a class of bodies which 
are soluble in water, which are not endowed with the capa- 
bility of propagating themselves, nor with any of the other 
properties distinctively characteristic of life, and which yet 
produce many effects closely related to those that are brought 
about by the micro-organisms called organized ferments. The 
new discoveries in connection with zymase, the enzyme ob- 
tained from yeast, make it seem possible, if not indeed prob- 
able, that the organized ferments produce their effect by 
means of the enzymes which they secrete. 

The enzymes were formerly classed as albuminous bodies, 
but the more recent study of some of them has made this view 
of their character improbable. In their chemical action the 
enzymes resemble the " catalytic " agents of inorganic chem- 
istry, which hasten a reaction between elements or compounds 
without themselves undergoing any apparent change, as 
when platinum hastens the union between hydrogen and 
oxygen. 

The more important classes of enzymes are : 

1. Proteolytic Enzymes, which convert protei'ds into pep- 
tones (see above). To this class belong pepsin, of the gastric 
juice, trypsin, secreted by the pancreas, and papayotin, found 
in certain plants. 

2. Amylolytic Enzymes, which convert starch into dextrin, 
maltose, or glucose, or which hydrolyze sugars. These are, 
diastase, formed in the germination of barley and other grains 
and found especially in malt ; ptyalin, found in the saliva, 



PTOMAINES. $17 

and acting in a similar manner but at a lower temperature ; 
amylopsin ox pancreatic diastase ; invertin, which is found in 
yeast, and which converts cane sugar to glucose and fructose. 

3. Enzymes which Decompose Fats, as steapsin, which is 
secreted by the pancreas, and which hydrolyzes fats to gly- 
cerol and fatty acids. 

4. Enzymes which Decompose Glucosides, as emulsin (p. 
182). 

5. Enzymes which Decompose Amides, as urase, which de- 
composes urea into carbonic acid and ammonia. 

6. Coagulating, as rennin, found especially in rennet, the 
mucous membrane of the stomach of the calf. It coagulates 
casein. 

7. Enzymes which Form Alcohols, as zymase, the enzyme 
of yeast (p. 131). 

Ptomaines. 

When albumin, flesh, or other animal or vegetable nitro- 
genous substances decay under the influence of bacteria, 
basic substances called ptomaines are often formed. Similar 
compounds seem to be formed in living animals and men 
during the progress of some diseases caused by pathogenic 
bacteria. Their formation, and the production of other toxic 
substances, undoubtedly plays a very important part in the 
progress of such diseases. 

The study of the ptomaines has acquired an especial 
interest, also, because a number have been discovered which 
give color reactions resembling some of the reactions of well- 
known poisonous alkaloids, a fact which has greatly in- 
creased the difficulty of the toxicological search for these 
poisons. 



5 IS ORGANIC CHEMISTRY. 

Some of the ptomaines are poisonous, others are not. 
Neurine (p. 433) and Cadaverine (1 ^-diaminopentane (p. 
433), have been mentioned. Methyl amine, dimethyl amine, 
and trimethyl amine have all been found in herring brine. 

Tetanine, C 13 H 20 N 2 O 4 , is formed when cultures of the 
bacteria of lockjaw, or tetanus, are made in horse-flesh. It 
is very poisonous. 

Typhotoxine, C 7 H 17 N0 2 , is obtained in a similar manner 
with the bacteria of typhus. It is poisonous. 

Erysipeline, C n H 13 N0 3 , has been found in the urine of 
persons affected with erysipelas. 

The list might be considerably extended. 

Toxins. 

In some, and perhaps in most of those diseases which are 
caused by bacteria, there are generated poisonous com- 
pdunds which appear to be closely related to the enzymes 
in their general character. These have been called tox- 
albumins by some authors, while other writers claim that 
they are not albumins, and prefer the more general name 
toxi?is. The latter term, in its broader sense, would include 
poisonous ptomaines as well. The poison of serpents, and 
the two vegetable poisons, abrin and ruin, which are of an 
albumin-like nature, seem, also, to be closely related to the 
toxins. Some of these bodies are very virulent. One-fourth 
of a milligram of the poison of tetanus is fatal to a guinea 
pig, while -Jq of a milligram of ricin per kilogram weight of 
the animal is fatal. Such results recall the fact that one 
part of rennin will coagulate two million parts of casein. 
None of the toxins of this class have been isolated in a pure 
condition, and the study of their chemical nature is attended 
with very great difficulty. 



FATS. 519 

Antitoxins. 

At the same time with the development of toxins under 
the influence of bacteria the animal organism appears to 
produce compounds which serve, in some manner which is 
little understood, as their antidotes. These are called anti- 
toxins. In a few cases, by inoculating animals with a 
particular disease, a blood serum can, later, be obtained 
which acts as a specific curative for that disease. The first 
of the antitoxins prepared in this manner, and the one 
which has, thus far, been most successful, was the antitoxin 
of diphtheria. 

Fats. 

From the physiological standpoint, the fats seem to be of 
value chiefly as a source, or for the storage of energy which 
can be converted into muscular work or heat. While the 
fatty acids are among the most stable of organic compounds, 
and are attacked only by very vigorous agents, the animal 
organism finds no difficulty, apparently, in securing their 
complete oxidation to carbon dioxide and water. 



INDEX. 



An asterisk after the number indicates that the compound is mentioned only in a table. 



Abrin, 518 

" Ac " as a prefix, 445 

Acenaphtene, 114* 

Acetal, 285 

Acetaldehyde, 175 

Acetaldehyde cyanhydrin, 178 

Acetamide, 299 

Acetanilide, 440 

Acetates, 227 

Acetic anhydride, 277 

Acetoacetic ester, 347 

Acetone, 187 

Acetone ethylmercaptol, 485 

Acetonitrile, 299 

Acetonylacetone, 207 

Acetophenone, 198 

Acetoxime, 189 

Acetylacetone, 206 

Acetyl chloride, 276 

Acetylene, 87 

Acetylidene, 87 

Acetyl trimethylene, 171* 

Acid, Acetic, 225 

Acetic sulphonic, 494 

Acetoacetic, 347 

Acetocoumaric, 497 

Acetonedicarboxylic, 337 

Aconitic, 337 

Acridic, 500 

Acrylic, 233 

Adipic, 256 

Allylacetic, 232 * 

Allocinnamic, 246 

Aminoacetic, 448 

Aminobenzoic, 451 

Aminocaproic, 450 

Aminocinnamic, 453 



Acid, Aminohydrocinnamic, 452 
Aminophenylacetic, 451 
Aminopropionic, 450 
Aminosuccinamidic, 450 
Aminotoluic, 451 
Angelic, 232* 
Anisic, 324 
Anthraflavinic, 215 
Anthranilic, 451 
Anthraquinone-sulphonic, 212, 

493 
Arachidic, 222 * 
Aspartic, 329, 450 
Azelaic, 238 
Behenic, 222* 
Benzene sulphonic, 491 
Benzoic, 241 
Benzoylbenzoic, 211 
Brombenzoic, 410 
Brommethylbutanoic, 394 
Brompropionic, 409 
Bromvaleric, 394 
Butanoic, 229 
Butanolic, 318 
Butyric, 229 
Camphanic, 260 
Campholytic, 261 
Camphoric, 196, 258 
Camphoronic, 196, 259 
Capric, 222* 
Caproic, 222* 
Caprylic, 222 * 
Carbamic, 292 
Carbolic, 142 
Carbonic, 313 
Chlorlactic, 326 
Chlorcrotonic, 235 



520 



INDEX. 



521 



Acid, Chloriso valeric, 393 
Cerotic, 223* 
Cinnamic, 244 
Cisbutenoic, 234 
Citraconic, 258, 337 
Citric, 335 
Coumaric, 331 
Cresolsulphonic, 340 
Crotonic, 234 
Cuminic, 325 

Cyclobutanecarboxylic, 232 * 
Cyclohexenoic, 240* 
Cyclopropane carboxylic, 232 * 
Cyclopropanedicarboxylic, 248 * 
Dehydromucic, 339 
Diaminocaproic, 512 
Diazoacetic, 463 
Dibrom acetic, 325 
Dibrommalonic, 328 
Dibromsuccinic, 334 
Dicetylacetic, 223* 
Dichloracetic, 408 
Dibydro-/3-campholytic, 232* 
Dihydroisolauronolic, 232* 
Dihydroterephthalic, 266 
Dihydroxybenzoic, 339 
Dihydroxysuccinic, 331 
Dimethyl acrylic, 232* 
Dimethylphenylhydroxypropi- 

onic, 243* 
Dimethylpropanoic, 222 * 
Dimethyl succinic, 248 * 
Dioxybrombenzoic, 340 
Dioxystearic, 239, 327 
Diphenylpropionic, 345 
Elaidic, 238 
Epihydrinic, 326 
Ethanediolic, 325 
Ethanoic, 225 
Ethenyl tricarboxylic, 254 
Ethoxyacetic, 315 
Ethylaminocinnamic, 455 
Ethyldithiocarbamic, 309 
Ethylene lactic, 317 
Ethylidene malonic, 234 
Ethylidene propionic, 232 * 
Ethyl malonic, 252 
Ethyl sulphonic, 490 
Formic, 223 



Acid, Formylacetic, 346 
Fulminic, 308 
Fumaric, 257 
Gallic, 160, 340 
Gluconic, 363 
Glutaconic, 258 
Glutaminic, 512 
Glutaric, 255 
Glyceric, 153, 326 
Glycidic, 326 
Glycolic, 313 
Glyoxylic. 325 
Hemellithic, 241 * 
Hexahydroisophthalic, 258, 265 
Hexahydroorthotoluic, 239 
Hexahydroterephthalic, 268 
Hexenoic, 237, 238 
Hippuric, 449 
Homocamphoric, 196 
Hydrocinnamic, 241 * 
Hydrocyanic, 302 
Hydrosorbic, 237 
Hydroxyacrylic, 346 
Hydroxybenzoic, 321, 323, 324 
Hydroxy butyric, 318 
Hydroxisocaproic, 319 
Hydroxyisopropylbenzoic, 325 
Hydroxymalonic, 327 
Hydroxypropionic, 315, 317 
Hydroxysuccinic, 328 
Hydroxytricarballylic, 325 
Hyenic, 223 * 
Iodopropionic, 409 
Isoanthraflavinic, 215 
Isobarbituric, 296 
Isobutyric, 229 
Isocamphoric, 249 * 
Isocaproic, 222 * 
Isocinnamic, 246 
Isocrotonic, 234 
Isodialuric, 296 
Isolauronolic, 240 * 
Isophthalic, 265 
Isosuccinic, 255 
Isovaleric, 230 
Isoxylic, 241 * 
Itaconic, 258, 337 
Lactic, 315 
Laurie, 222 * 



522 



INDEX. 



Acid, Levulinic, 355 
Lignoceric, 223* 
Malonic, 251 
Mannonic, 363 
Male'ic, 257 
Malic, 328 
Margaric, 222* 
Monochloracetic, 407 
Melissic, 223* 
Mesaconic, 258 
Mesitylenic, 241 * 
Mesotartaric, 157, t,33 
Mesoxalic, 153, 328 
Methacrylic, 232* 
Methanoic, 223 

Methoethylolphenmethylic, 325 
Methylbutanoic, 230 
Methylbutenoic, 232 * 
Methylbutylacetic, 365 
Methylcinnamic,' 245 
Methylcyclohexane-carboxylic, 

239 
a-Methylglutaric, 253 
Methylhydroxypentanoic, 319 
Methylmalonic, 255 
Methylpropanoic, 229 
Methylpropenoic, 232* 
Methyl succinic, 248 
Mucic, 339 
Myristic, 222 * 
Myronic, 377 

Naphthalene sulphonic, 493 
Nicotinic, 439, 447 
Nitrobenzoic, 416, 417 
Nitrocinnamic, 417 
Nitrophenylpropiolic, 418 
Nitrotartaric, 327 
Nitrouracilcarboxylic, 295. 
Nondecylic, 222 * 
Octadecenoic, 232* 
Oenanthylic, 222 * 
Oleic, 238 
Oxalic, 249 

Oxybenzoic, 321, 323, 324 
Oxypivalinic, 245 
Palmitic, 230 
Parabanic, 294 
Pelargonic, 238 
Pentadecylic, 222* 



Acid, Pentanonic, 355 
Pentenoic, 232 * 
Phenyl acetic, 241 * 
Phenylcrotonic, 245 
Phenylglyoxylic, 346 
Phenylolhydroxypropionic, 331 
Phenylpropiolic, 247 
Phloretic, 377 
Phthalamidic, 299 
Phthalic, 261 
Phthalonic, 261, 346 
Pimelic, 257 
Piperic, 187 

Propanedioldiacid, 1 53. 
Propanediolic, 153, 326 
Propanoic, 228 
Propanoldiacid, 153 
Propanolic, 315, 317 
Propanonic, 344 
Propenoic, 233 
Propenylbenzoic, 325 
Propinoic, 240* 
Propiolic, 240 * 
Propionic, 228 
Propylidene acetic, 332 * 
Protocatechuic, 86, 339 
Pyridine carboxylic, 439 
Pyroligneous, 225 
Pyromucic, 339 
Pyroracemic, 344 
Pyrotartaric, 248 * 
Pyroterebic, 232 * 
Quinoline dicarboxylic, 500 
Quinolinic, 446 
Racemic, ^33 
Saccharic, 338 
Salicylic, 321 
Sebacic, 248 * 
Sorbic, 237 
Stearic, 230 
Stearolic, 238 
Stearoxylic, 238 
Suberic, 248* 
Succinic, 254 
Sulphanisic, 340 
Tartaric, 331 
Tartronic, 153, 327 
Tetrahydrobenzoic, 240 * 
Tetrahydroterephthalic, 267 



INDEX. 



523 



Acid, Terephthalic, 265 

Tetrolic, 240 * 

Tiglic, 232 * 

Toluic, 240* 

Transbutenoic, 234 

Triazoacetic, 463 

Trichloracetic, 408 

Trichlorcyclopentenediolcarbox- 
ylic, 146 » 

Tridecylic, 222 * 

Trimethylcyclopentanecarbox- 
ylic, 232 * 

Trimethylcyclopentenoic, 240* 

Trimethylsuccinic, 259 

Trimethyltricarballylic, 196 

Undecylic, 222* 

Uric, 293 

Valeric, 230 

Vanillic, 340 

Xylic, 241 * 
Acid anhydrides, 276 
Acid chlorides, 273 
Acid decomposition, 351 
Acids, 220 

preparation of, 270 
Aconitine, 508 
Acridine, 499 
Acridone, 500 
Acrolein, 180 
Acrose, 174 
Adipic ester, 256 
Adipic ketone, 171 * 
Adjective dyes, 481 
Aesculetin, 375 
Aesculin, 375 
Alanine, 450 
Albumins, 510 
Albumoid, 510* 
Albumoses, 513 
Alcohol, 129 ff. 
Alcohol, absolute, 132 
Alcohols, 124, 126 

preparation of, 161 
Aldehyde acids, 344 
Aldehyde ammonia, 179 
Aldehydes, 170, 218 

preparation of, 215 
Aldohexoses, 357 
Aldol, 177 



Alicyclic compounds, 117 
Aliphatic compounds, 93 
Alizarin, 212 
Alkaloids, 299, 502 
Alloisomerism, 235 
Alloxan, 293 
Alloxantin, 294 
Allyl alcohol, 140 
Allyl bromide, 400 
Allylene, 87 * 
Allyl ether, 164* 
Allylmethoxybenzene, 324 
Allylpyridine, 435 
Ally! thiocyanate, 310 
Amide chlorides, 310 
Amides, 286 
Amidines, 311 
Amido group, 288 
Amidoximes, 311 
Amines, 420 
Aminoazobenzene, 467 
Aminoazo compounds, 466 
Aminocyclopentane, 424 
Amino group, 289 
Aminophenol, 209 
Aminouracil, 296 
Ammonium thiocyanate, 308 
Amygdalin, 182, 302, 376 
Amyl alcohols, 136 
Amylan, 358* 
Amylopsin, 517 
Amyloid, 510* 
Amylum, 373 
Anaesthetics, 397 
Analysis, 19 
Anethol, 324 
Anhydrides, acid, 276 
Aniline, 439 
Aniline yellow, 468 
Anisol, 166 
Anthracene, 117 
Anthrahydroquinone, 214 
Anthranol, 149, 214 
Anthranone, 214 
Anthrapurpurin, 215 
Anthraquinone, 211 
Anthrarufin, 215 
Anthrol, 149, 214 
Anti-benzaldoxime, 183 



524 



INDEX. 



Antifebrine, 440 
Antipyrine, 499 
Antitoxins, 519 
Arabin, 375 
Arabinose, 360 
" Ar" as a prefix, 445 
Arginine, 512 
Argol, 331 

Aromatic compounds, 93 
Asparagine, 450 

Asymmetry of nitrogen com- 
pounds, 432 
Atropine, 503 
Auxochrome groups, 480 
Azobenzene, 473 
Azo compounds, 456 
Azoxybenzene, 471 
Azoxy compounds, 471 

Beckmann's rearrangement, 200 
Benzalacetone, 190 
Benzaldehyde, 182 
Benzaldoxime, 183 
Benzamide, 299 
Benzdioxyanthraquinone, 215 
Benzene, 93 ff., 107 
Benzene diazonium chloride, 458 
Benzenedisazobenzene, 472 
Benzidine, 444 
Benzil, 185, 203 
Benzine, 73 
Benzoic anilide, 200 
Benzoic sulphamide, 492 
Benzoic sulphinide, 492 
Benzoic toluide, 201 
Benzoin, 185 
Benzophenone, 199 
Benzoquinone, 172* 
Benzotrichloride, 242 
Benzoyl chloride, 276 
Benzoylglycocoll, 449 
Benzyl alcohol, 148 
Benzyl amine, 415, 443 
Benzyl bromide, 403 
Berberine, 507 
Betai'n, 449 

Bitter almonds, oil of, 182 
Bitter principles, 378 
Boiling-point, 18, rise of, 32 



Borneol, 142, 196 
Bromanthraquinone, 212 
Bromethylene, 399 
Bromhydrins, 493 
Bromisocaproic ester, 394 
Bromoform, 396 
Brompropylenes, 400 
Bromtoluenes, 401, 402 
Brucine, 506 
Butadiene, 87 * 
Butanal, 170* 
Butanedione, 203 
Butanolid, 319 
Butanes, 66 
Butanetetrol, 125* 
Butanols, 135 
Butanone, 171 * 
Butenal, 181 
Butenes, 75 *, 80 
Butenols, 124* 
Butines, 87 * 
Butyl alcohols, 135 
Butyric aldehyde, 170* 
Butyrolactone, 319 
"Bz" as a prefix, 453 

Cadaverine, 433 
Caffeine, 298 
Camphene, 401 
Camphor, 195, 259 

artificial, 401 
Camphorphorone, 171* 
Cane sugar, 367 
Capillarity, 43 
Caproic aldehyde, 170* 
Caprolactone, 237 
Carbamic chloride, 292 
Carbamide, 290 
Carbanilide, 304 
Carbohydrates, 357 
Carbon tetrachloride, 397 
Carbostyril, 453 

Carboxethyl cyclohexanone, 354 
Carboxethyl cyclopentanone, 352 
Carboxyl group, 220 
Carbylamines, 304 
Carone, 197 
Caro's reagent, 195 
Carvacrol, 148 



INDEX. 



525 



Carvenone, 197 

Casein, 513 

Cellulose, 371 

Cetyl alcohol, 124 * 

Chloral, 405 

Chloral hydrate, 406 

Chlorcarbonic ester, 286 

Chlorethane, 398 

Chlorethanol, 168, 40*4 

Chlorformic ester, 286 

Chlorhydrins, 403 

Chlormalonic ester, 327 

Chloroform, 396 

Chlorpropanediol, 404 

Chlorquinoline, 453 

Choline, 433 

Chromophore groups, 480 

Chrysene, 114* 

Cinchonine, 506 

Cinnamic aldehyde, 171* 

Cis forms, 236 

Citral, 181 

Claus's formula, 103 

Cocaine, 504 

Codeine, 507 

Collagens, 515 

Collidine, 438 

Color, 47 

Combustion, heat of, 44, 80, 

85 
Conductivity, electrical, 49 
" Congo" dyes, 475 
Coniferin, 376 
Coni'ine, 435, 503 
Copper carbide, 88 
Coumarin, 496 
Coumarone, 497 
Cream of tartar, 331 
Creatine, 512 
Creosote, 147 
Cresol, 147 

Critical temperature, 44 
Crotonic aldehyde, 181 
Crotyl alcohol, 124* 
Crysazin, 215 
Crysazol, 214 
Crysom, 471 
Crystalline form, 10 
Crystallization, 9 



Cumene, 107* 
Cuminic aldehyde, 171 * 
Curarine, 508 
Cyanamide, 304 
Cyanates, 306 
Cyanides, 300 
Cyanogen chloride, 303 
Cyanuric chloride, 304 
Cyclic alcohols, 142 
Cyclic hydrocarbons, 82 
Cyclobutane, 83 
Cyclobutanol, 124* 
Cycloheptane, 85 
Cycloheptanol, 125* 
Cycloheptanone, 192 
Cyclohexadienedione, 172* 
Cyclohexane, 85 
Cyclohexanedione, 159, 207 
Cyclohexanol, 124* 
Cyclohexanone, 192 
Cyclohexenolone, 159 
Cyclopentane, 84 
Cyclopentanol, 142 
Cyclopentanone, 192 
Cyclopentene aldehyde, 170* 
Cyclopropane, 83 
Cyclooctane, 85 
Cymogene, 73 
Cymene, no, 196 

Decahydronaphthalene, 90 
Decane, 70 

Derivatives, classification of, 12: 
Dextro compounds, 137 
Dextrin, 374 
Dextrose, 361 
Diacetyl, 203 

Diacetylsuccinic ester, 207 
Diacetyltartaric ester, 332 
Diaminobenzene, 209 
Diaminodiphenyl, 444 
Diaminonaphthalene, 446 
Diastase, 516 
Diazoacetic ester, 462 
Diazoaminobenzene, 466 
Diazobenzene, 479 
Diazobenzene imide, 479 
Diazobenzene potassium, 457 
Diazo compounds, 456 



526 



INDEX. 



Diazo group, replacement of, 459 
Diazoimides, 478 
Diazonium salts, 456 
Dibenzalacetone, 190 
Dibrombutanediols, 156 
Dibrompropane, 401 
Dichlorethanes, 78, 398 
Dichlorhydrin, 405 
Dichlorpropanol, 405 
Dicyclic compounds, 90 
Diethyl carbonate, 284 
Diethyl ketone, 171* 
Diethylsulphone, 486 
Diethylsulphone-dimethylme- 

thane, 486 
Diformin, 140 
Digitalei'n, 376 
Digitaliretin, 376 
Dihydroresorcinol, 207 
Dihydroxyanthracene, 214 
Dihydroxyanthraquinones, 2 1 5 
Dihydroxybenzene, 158 
Dihydroxyxylene, 211 
Diiodomethane, 395 
Dimethyl amine, 429 
Dimethyl aminoazobenzene, 468 
Dimethyl aniline, 429, 442 
Dimethyl azole, 208 
Dimethyl butanes, 56*, 75 * 
Dimethyl butanone, 189 
Dimethyl cyclohexanes, 82 * 
Dimethylene imine, 432 
Dimethyl furane, 208 
Dimethyl furfurane, 208 
Dimethyl heptane, 56* 
Dimethyl hexane, 56* 
Dimethyl ketone, 187 
Dimethyloctadienal, 181 
Dimethyl octanes, 56* 
Dimethyl pentane,56* 
Dimethyl propane, 68 
Dimethyl pyridines, 438 
Dimethyl pyrrol, 208 
Dimethyl thiofurane, 208 
Dimethyl thiophene, 208 
Dimethyl xanthine, 298 
Diminished pressure, distillation 

under, 16 
Dinitrobenzene, 414 



Dioxindol, 451 
Dioxyanthracene, 214 
Dioxyanthraquinones, 215 
Dioxyterephthalic ester, 355 
Dioxyuracil, 296 
Diphenyl, 114* 
Diphenylethanedione, 172* 
Diphenylethanes, 114* 
Diphenylfurazane, 185 
Diphenylmethane, 114* 
Diphenylquinoxaline, 203 
Diphenylsulphone, 486 
Diphenyl urea, 304 . 
Dipropargyl, 87 * 
Disaccharides, 367 
Disazo compounds, 472 
Dissociation constants, 409, 417, 

424 
Distillation, 12 ff. 
Dithioethyldimethylmethane, 485 
Double unions, 79 
Dumas's method, 23 
Dulcite, 158 
Durene, 107 * 
Dyes, 479 
Dynamite, 154 

Ecgonine, 505 

Egg albumin, 509 * 

Eikosane, 70 

Elastins, 515 

Emetine, 508 

Empirical formulae, 21 

Emulsin, 302, 517 

" Enol " form, 205 

Enzymes, 516 

Eosin, 265 

Erysipeline, 518 

Erythrol, 154 

Esterification, law of, 280 V 

Esters, 278 L 

Ethanal, 175 

Ethane, 61 

Ethanediol, 150 

Ethanethiol, 483 

Ethanol, 129 

Ethanoyl cyclopropane, 171 * 

Ethene, 76 

Ethenol, 139 



INDEX. 



527 



Ethers, 164 

Ethoxyacetic ester, 315 
Ethyl acetate, 278 
Ethyl amines, 431 
Ethyl alcohol, 129 
Ethyl benzene, 109 
Ethylbenzyl hydroxylamine, 448 
Ethyl bromide, 399 c 
Ethyl butyrate, 284 
Ethyl carbamate, 292 
Ethyl carbonimide, 307 
Ethyl chloride, 398 
Ethyl cyanate, 396 
Ethylene, 76 
Ethylene bromide, 399 
Ethylene chloride, 398 
Ethylene oxide, 168 
Ethylene series, 75 
Ethyl ether, 165 
Ethyl glycollate, 315 
Ethyl hydroxylamine, 448 
Ethylidene acetone, 171 * 
Ethylidene chloride, 398 
Ethylidenediethyl ether, 285 
Ethyl iodide, 400 
Ethyl isocyanate, 307 
Ethyl mercaptan, 483 
Ethyl nitrite, 41 1 

Ethylol trimethyl ammonium hy- 
droxide, 433 
Ethylonephen, 172* 
Ethylpentane, 56* 
Ethyl phenyl ether, 166 
Ethylphenyl ketone, 172* 
Ethyl pseudocarbostyril, 454 
Ethyl pyridines, 438 
Ethyl quinolone, 454 
Ethyl sulphide, 484 
Ethyl sulphuric acid, 76 
Ethyl thiocyanate, 308 
Eugenol, 186 

Fast colors, 482 
Fatty acids, 222 
Fats, 519 

Fehling's solution, 363 
Fenchone, 197 
Fermentation, 130 
Ferments, soluble, 516 



Fibrin, 513 
Fibrinogen, 513 
Fittig's synthesis, in 
Flavol, 214 
Flavopurpurin, 215 
Flashing-point, 73 
Fluorene, 114* 
Fluorescein, 264 
Formaldehyde, 173 
Formaline, 174 
Formation, heat of, 45 
Formulae, graphical, 65 
Fractional distillation, 13 
Freezing point lowering, 26 ff. 
Friedel-Craft reaction, 112 
Fructose, 365 
Fruit sugar, 365 
Fuchsine, 442 
Furfural, 360 

Galactose, 357 * 

Gasoline, 73 

Gelatine, explosive, 154 

Gelsemine, 508 

Geranial, 181 

Geraniol, 181 

Globin, 515 

Globulins, 512 

Glucoheptose, 358* 

Gluconic anhydride, 364 

Glucononose, 358* 

Glucosazone, 364 

Glucose, 361 

Glucosides, 357, 375 

Glutaric anhydride, 256 

Gluten protein, 509 * 

Glycerine, 152 

Glycerol, 152 

Glycerol trinitrate, 154 

Glycine, 448 

Glycocoll, 448 

Glycogen, 374 

Glycol, 150 

Glycol chlorhydrin, 168, 404 

Glycolic acetate, 315 

Glycolic aldehyde, 151 

Glycolid, 3 1 5 

Glycol monacetate, 168 

Glycoproteins, 515 



528 



INDEX. 



Glyoxal, 152 
Grape sugar, 361 
Guaiacol, 186 
Guanine, 299 
Gulose, 366 
Gun-cotton, 372 

Haematin, 515 
Haemin, 515 
Haemoglobin, 514 
Halogen compounds, 380 
Halogens, determination, 21 
Helianthin, 468 
Helicin, 378 
Helicoprote'id, 510* 
Hemellithene, 107 * 
Heptanal, 170* 
Heptane, 56* 

Heterocyclic compounds, 495 
Hexachlorethane, 398 
Hexadiines, 87 * 
Hexahydropyridine, 434 
Hexahydroxycyclohexane, 367 
Hexamethylene amine, 174 
Hexanal, 170 * 
Hexanedione, 207 
Hexanehexols, 158 
Hexanes, 68 
Hexanetrione, 160 
Hexazane, 434 
Kexenes, 75 * 
Hexoses, 357 

Hexoxyhexahydrobenzene, 367 
Histone, 510 * 
Hofmann's method, 26 
Homology, 56 
Hydrastine, 507 
Hydrazines, 476 
Hydrazobenzene, 476 
Hydrazo compounds, 473 
Hydrazones, 179, 478 
Hydrindene, 114* 
Hydroanthranol, 214 
Hydrocarbons, 55 
Hydrocarbostyril, 453 
Hydrocinnamic aldehyde, 170 * 
Hydropyrone, 190 
Hydroquinone, 160 
Hydroxy acids, 3 1 3 



Hydroxyanthraquinone, 212 
Hydroxyazobenzene, 470 
Hydroxyazo compounds, 469 
Hydroxybenzaldehydes, 1 85 
Hydroxybenzyl alcohol, 378 
Hydroxydisazo compounds, 470 
Hydroxylamine derivatives, 447 
Hydroxyl group, 129 
Hydroxyquinoline, 453 
Hydroxytoluene, 147 
Hystarin, 215 

Imide chlorides, 310 

Imides, 289 

Imido esters, 310 

Inactive compounds, 137 

Indene, 114 * 

Indican, 376 

Indiglucin, 377 

Indigo, 451 

Indol, 452 

Indophenin reaction, 495 

Indurite, 373 

Inosite, 367 

Inulin, 374 

Invertin, 517 

Invert sugar, 365 

Iodoform, 396 

Iodopropane, 400 

Ionone, 182, 197 

Iridin, 377 

Irigenin, 377 

Irone, 197, 377 

Isatine, 451 

Isoamyl acetate, 284 

Isoamyl alcohol, 136 

Isoamyl ether, 164 * 

Isoamyl isovalerate, 284 

Isobutane, 66 

Isobutyl alcohol, 135 

Isobutyric aldehyde, 170 * 

Isocaprolactone, 320 

Isocyanates, 306 

Isocyanides, 304 

Isodiazobenzene potassium, 457 

Isomaltose, 358 * 

Isomerism, 64 

Isomerism, geometrical, 156 

Isonitriles, 304 



INDEX. 



529 



Isonitrosoketones, 201 
Isopentane, 68 
Isopropyl alcohol, 135 
Isopropyl benzenes, 107 * 
Isopropyl ether, 164 * 
Isopropyl iodide, 400 
Isoquinoline group, 506 
Isothiocyanates, 309 
Isovaleric aldehyde, 170* 

Jervine, 508 

Kekule's formula, 103 
Keratins, 515 
Kerosene, 73 
Ketohexoses, 357 
Ketones, 170, 218 
Ketones, preparation of, 216 
Ketonic acids, 344 
'Ketonic decomposition, 202, 351 
Kjeldahl method, 20, 

Lact albumin, 509* 
Lactid, 317 
Lactoglobulin, 509* 
Lactose, 370 
Lactosin, 358* 
Ladenburg's formula, 101 
Laevo compounds, 137 
Lakes, 213 
Laudanum, 507 
Lecithin, 433 
Leucine, 450 
Leuco compounds, 473 
Liebermann's reaction, 427 
Ligroin, 73 
Lobeline, 508 
Lutidines, 438 
Lysine, 512 

Magnetic rotation, 49 
Malei'c anhydride, 257 
Malonic ester, 251 
Maltose, 370 
Mannite, 158 
Mannoheptose, 358* 
Mannononose, 358* 
Manno-octose, 358* 
Mannose, 363 



Marsh-gas, 58 

Marsh-gas series, 55 

Melibiose, 358* 

Melitose, 371 

Melitriose, 371 

Melezitose, 358* 

Melting-point determinations, 10 

Menthone, 195 

Mercaptans, 483 

Mesitylene, no, 191 

Mesityl oxide, 192 

Metaformaldehyde, 174 

Metaldehyde, 176 

Meta position, 105 

Methanal, 173 

Methane, 58 

Methanol, 126 

Metho-ethylphenmethylal, 171* 

Methyl alcohol, 126 

Methylalcyclopentane, 170* 

Methylalcyclopentene, 170* 

Methyl amine, 429 

Methyl aniline, 441 

Methyl benzamide, 201 

Methylbenzimidazole, 443 

Methylbenzyl ketone, 172* 

Methyl butanal, 170* 

Methyl butane, 68 

Methyl-butanols, 136 

Methyl butanone, 171 * 

Methyl butenal, 170* 

Methylbutenes, 75* 

Methyl butenone, 171* 

Methylcarboxethylcyclopenta- 

none, 353 
Methyl cyanide, 299 
Methyl cyclobutane, 83 
Methyl cyclohexane, 82 * 
Methyl cyclopentane, 86 
Methyl cyclopentenone, 171 * 
Methyl cyclopropane, 82 * 
Methylene, 76 
Methylene iodide, 395 
Methyl ether, 164* 
Methyl ethyl ether, 164* 
Methyl ethyl ketone, 171 * 
Methylethylthetin, 488 
Methylethylthetin bromide, 487 
Methylglycocoll, 449 



53Q 



INDEX. 



Methyl hexanes, 56* 

Methyl hexazane, 435 

Methyl hydroxylamine, 447 

Methyl iodide, 395 

Methyl isopropylbenzene, 196 

Methyl isopropyl ketone, 171 * 

Methylnonane, 56 * 

Methyl orange, 468 

Methyl pentanes, 56* 

Methyl pentanolid, 320 

Methyl pentenes, 75 * 

Methyl pentenone, 171 * 

Methyl phenmethylal, 170* 

Methyl phenyl ether, 166 

Methylpiperidine, 435 

Methyl propanal, 170* 

Methyl propane, 66 

Methyl propanol, 135 

Methyl propargyl ether, 164* 

Methyl propene, 75* 

Methyl propyl cyclohexanone, 171* 

Methyl propyl ether, 164*. 

Methyl propyl ketone, 171 * 

Methyl pyridines, 438 

Methyl salicylate, 323 

Methyl uracil, 295 

Methyl violet, 442 

Meyer's law of esterification, 280 

Meyer's vapor density method, 25 

Milk sugar, 370 

Molecular dispersion, 47 

Molecular refraction, 46 

Molecular volume, 40 

Molecular weight, determination, 

22 ff. 
Monochlorhydrin, 404 
Monoethyl carbonate, 284 
Monoformin, 224 
Mordants, 213, 481 
Morphine, 507 
Mucin, 510* 
Mucoid, 510* 
Multirotation, 362 
Mustard oils, 309 
Myogen, 509* 
Myosin, 509* 

Naphtha, 73 
Naphthaldehyde, 171 * 



Naphthalene, 116 
Naphthenemethylal, 171* 
Naphthols, 149 
Naphthoquinones, 173* 
Naphthylamine, 444 
Naphthyl ether, 164* 
Narceine, 507 
Narcotine, 507 
Natural gas, 58 
Nervanine, 505 
Neurine, 433 
Nicotine, 438, 503 
Nitriles, 300 
Nitrobenzene, 413 
Nitrobenzene diazonium chloride, 

458 
Nitrocellulose, 372 
Nitro compounds, 411 
Nitroethane, 411 
Nitrogen, determination, 20 
Nitroglycerine, 154 
Nitronaphthalene, 416 
Nitrophenols, 416 
Nitrosamines, 426 
Nitrosophenol, 210 
Nitrosopiperidine, 434 
Nitrotoluenes, 414, 415 
Nitrourea, 418 
Nitroxylenes, 415 
Nonane, 56 * 
Nucle'ins, 514 
Nuclec albumins, 513 
Nucleoprote'ids, 514 

Octane, 70 
Octyl acetate, 284 
Oenanthaldehyde, vjo * 
Official nomenclature, 68 
Oil of anise, 324 
Oil of wintergreen, 323 
Olefiant gas, 77 
Olei'n, 152, 238 
Opium, 506 
Optical activity, 137 
Orange III, 468 
Ornithine, 512 
Orthocarbonic ester, 285 
Orthoform, 505 
Orthoformic ester, 28? 



INDEX. 



531 



Ortho position, 105 
Osazones, 364, 478 
Overcooling, 10, 30 
Oxalates, 250 
Oximes, 179 
Oxindol, 451 
Oxyanthraquinone, 214 
Oxyanthrarufin, 215 
Oxyazobenzene, 470 * 
Oxyazo compounds, 469 
Oxym ethylene, 174 
Oxy uracil, 296 

Palmitin, 152, 230 
Papaverine, 507 
Papayotin, 516 
Paraffin, 73 
Paraffin oils, 7 2 
Paraffins, 56, 70 
Paraldehyde, 176 
Para position, 105 
Paregoric, 507 
Pentachlorethane, 398 
Pentamethylene diamine, 433 
Pentamethylene oxide, 164* 
Pentanedione, 206 
Pentanes, 67 
Pentanol, 124* 
Pentanone, 171* 
Pentazane, 437 
Pent en es, 75 * 
Pentenone, 171* 
Pentosans, 375 
Pentoses, 357 
Pentylene oxide, 164* 
Pepsin, 516 
Peptones, 513 
Perbromethylene, 399 
Perkin's synthesis, 244 
Petroleum, 71 
Petroleum ether, 73 
Phenanthrene, 119 
Phenanthrenequinone, 204 
Phendiols, 158, 160 
Phenethylal, 170* 
Phenetol, 166 
Phenmethylal, 170* 
Phenmethylol, 125* 
Phenol, 142 



Phenoldisazobenzene, 470 
Phenolphthalei'n, 263 
Phenpropenylal, 171* 
Phenpropylal, 170* 
Phenthiol, 484 
Phentriols, 160 
Phenyl acetaldehyde, 170* 
Phenyl acetamide, 440 
Phenyl acetylene, 247 
Phenyl carbonimide, 307 
Phenyl cyclotriazine, 479 
Phenyl cyanide, 241 
Phenyldimethyl pyrazole, 206 
Phenyldimethylpyrazolone, 499 
Phenylene diamines, 443, 444 
Phenyl ether, 164* 
Phenyl hydrazine, 477 
Phenyl isocyanate, 307 
Phenyl isocyanide chloride, 304 
Phenyl isothiocyanate, 305 
Phenyl methylamine, 441 
Phenyl methyl ketone, 198 
Phenyl methylpyrazolone, 499 
Phenyl mustard oil, 305 
Phenyl nitromethane, 415 
Phenyl pyrazole, 498 
Phenyl sulphide, 485 
Phenyl thioformamide, 305 
Phenyl tolyl ketoxime, 201 
Phenyl urethane, 293 
Phloretin, 377 
Phlorizin, 377 
Phloroglucinol, 160 
Phorone, 192 

Phthalic anhydride, 262, 278 
Phthalid, 262, 325 
Phthalimide, 289 
Phthalyl chloride, 262 
Phytovitellin, 509 * 
Picoline, 438 
Pilocarpine, 503 
Pimelic ester, 354 
Pimelic ketone, 171 * 
Pinacoline, 189 
Pinacone, 188 
Pinene hydrochloride, 401 
Pipecoline, 435 
Piperidine, 434 
Piperine, 503 



532 



INDEX. 



Piperonal, 187 
Polarization, circular, 47 
Potassium cyanide, 302 
Potassium ferrocyanide, 303 
Potassium thiocyanate, 308 
Prism formula, 101 
Propadiene, 87 * 
Propanal, 170 
Propane, 62 
Propanediol, 152 
Propanediol, 152 
Propanols, 134, 135 
Propanone, 187 
Propargyl alcohol, 125 * 
Propenal, 180 
Propene, 75 * 
Propenol, 124 * 
Propinol, 125 * 
Propionic aldehyde, 1 70 * 
Propionyl chloride, 275 
Protamine, 510 * 
Proteins, 509 
Propyl alcohol, 134 
Propylene glycol, 1 52 
Propylene oxide, 164 * 
Propyl ether, 164 * 
Propyl iodide, 400 
Propylonephen, 172 * 
Propyl piperi dine, 435 
Pseudo acids, 411 
Pseudo compounds, 454 
Pseudocumene, no 
Ptomaines, 433, 517 
Ptyalin, 516 
Pulegone, 197 
Purification, 9 
Purpurin, 215 
Purpuroxanthin, 215 
Putrescine, 512 
" Py " as a prefix, 453 
Pyrazole, 497 
Pyrazolone, 498 
Pyridine, 437 
Pyridine group, 503 
Pyrocatechol, 158 
Pyrogallol, 1 60 
Pyrone, 190 
Pyroterebic ester, 394 
Pyroxylin, 372 



Pyrrol, 436 
Pyrrolidine, 437, 504 
Pyrroline, 437 

Quaternary ammonium bases, 420 
Quinazarin, 215 
Quinidine, 506 
Quinine, 505 
Quinoline, 446 
Quinoline group, 505 
Quinoline iodoethylate, 455 
Quinone monoxime, 210 
Quinones, 209 

Racemic compounds, 138 
Raffinose, 371 

Reimer-Tiemann reaction, 186 
Rennin, 517 
Resorcinol, 158 
Resorcinoldisazobenzene, 472 
Rhamnoheptose, 358* 
Rhamnohexose, 358* 
Rhamnose, 357 * 
Rhigolene, 73 
Ricin, 513 

Rings, formation of, 193 
Rochelle salt, 335 
Rosaniline, 442 
Rufol, 214 

Saccharates, 369 

Saccharin, 492 

Saccharose, 367 

Salicin, 378 

Salicylic aldehyde, 185 

Saligenin, 186 

Sandmeyer's reaction, 460 

Sapogenin, 378 

Saponification, 152, 283 

Saponin, 378 

Sarcosine, 449 

Schotten-Baumann reaction, 282 

Schweitzer's reagent, 372 

Semicarbazones, 179 

Semidines, 474 

Serum albumin, 509 * 

Sinigrin, 377 

Soap, 152, 230 

Sodium glycolate, 15 1 



INDEX. 



533 



Solanidine, 378 

Solanine, 378 

Sorbinose, 357* 

Sorbite, 158 

Space arrangement, 66 

Specific gravity, 39 

Spongin, 510* 

Starch, ^73 

Starch sugar, 361 

Steam distillation, 17 

Steapsin, 517 

Stearin, 152, 230 

Stereoisomerism, 156, 183, 236, 239 

Strychnine, 506 

Styrene, 114* 

Suberone, 192 

Substantive dyes, 481 

Succinimide, 289 

Succinylosuccinic ester, 354 

Sulfonal, 486 

Sulphides, 484 

S ulphobenzenazonaphthylamine, 

445, 469 
Sulphodihydroxyazobenzene, 471 
Sulphodimethylaminoazobenzene, 

468 
Sulphones, 486 
Sulphonic acids, 488 
Sulphonium bases, 487 
Sulphotoluene, 491 
Sulphur compounds, 483 
Sulphur, determination, 21 
Sulphur ethers, 484 
Surface tension, 43 
Syn-benzaldoxime, 183 

Tanacetone, 197 
Tannins, 341, 376 
Tartar emetic, 335 
Tautomerism, 297 
Terpenes, 91 
Tetanine, 518 
Tetrabromfluorescem, 265 
Tetrachlorethane, 398 
Tetrahydronaphthylamines, 445 
Tetramethyl ammonium iodide, 

431 
Tetramethyl benzene, 107* 
Tetramethylene aldehyde, 170* 



Tetramethyl methane, 68 
Tetrethyl ammonium hydroxide, 

431 
Tetrose, 359 
Tetroxalates, 250 
Thebai'ne, 507 
Thei'ne, 298 
Theobromine, 298 
Thetin compounds, 487 
Thioalcohols, 483 
Thiocyanates, 308 
Thioformanilide, 305 
Thiophene, 495 
Thiophenol, 484 
Thiotolene, 495 
Thioxene, 495 
Thujone, 197 
Thymol, 148 
Tiglic aldehyde, 1 70 * 
Toluene, 108 
Toluene sulphamide, 492 
Toluene sulphochloride, 492 
Toluic aldehyde, 170* 
Toluic anilide, 201 
Toluidines, 442 
Toxalbumins, 518 
Toxins, 518 
Trans forms, 236 
Trehalose, 358* 
Triaminoazobenzene, 468 
Triazobenzene, 479 
Tribrommethane, 396 
Tribromphenol, 405 
Trichloracetaldehyde, 405 
Trichlorethane, 398 
Trichlorhydrin, 405 
Trichlormethane, 396 
Trichlorpropane, 405 
Triethyl sulphonium hydroxide, 

487 
Triethyl sulphonium iodide, 487 
Triiodomethane, 396 
Trimethyl amine, 430 
Trimethyl benzenes, 107* 
Trimethyl cyclopentanone, 260 
Trimethylene bromide, 401 
Trimethylene glycol, 132 
Trimethyl glycocoll, 449 
Trimethyl pyridine, 438 



534 



INDEX. 



Trimethylxanthine, 298 
Trinitrobenzene, 414 
Triphenylcarbinol, 263 
Triphenylchlormethane, 403 
Triphenylmethane, 115 
Triphenylmethyl, 115 
Trioxyanthraquinones, 215 
Trisaccharides, 371 
Tropaolin D, 468 
Tropaolin O, 471 
Trypsin, 516 
Turanose, 358* 
Turkey red, 212 
Typhotoxine, 518 

Unsaturated hydrocarbons, 75, 77 

Uracil, 294 

Uramidocrotonic ester, 295 

Urase, 517 

Urea, 290 

Urea chloride, 292 

Urethane, 292 

Valeric aldehyde, 1 70 * 
Valerolactone, 394 



Valylene, 87* 
Vanillin, 186 

Vapor density, determination, 23 
Vaseline, 73 
Veratrine, 508 
Vinegar, 226 
Vinyl alcohol, 139 
Vinyl amine, 432 
Vinyl bromide, 399 
Vinyl ether, 164 * 
Vinyl trimethyl ammonium hydrox- 
ide, 433 
Viscosity, 43 
Vitellin, 509 * 

Wood alcohol, 126 

Xanthine, 298 

Xylan, 360, 375 

Xylene diazonium chloride, 458 

Xylenes, 109 

Xylidines, 442 

Xyloquinone, 211 

Xylose, 360 

Zymase, 517 



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